The effect of genotype and rearing system on chicken meat

The effect of genotype and rearing system on chicken meat quality

by Sunett Joubert

December 2013

Thesis presented in fulfilment of the requirements for the degree of Master of Science in Food Science in the Faculty of AgriSciences at

Stellenbosch University

Supervisor: Prof LC Hoffman Co-supervisor: M. Muller. E.Pieterse

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DECLARATION

By submitting this thesis electronically, I declare that the entirety of the work contained therein is

my own, original work, that I am the sole author thereof (save to the extent explicitly otherwise

stated), that reproduction and publication thereof by Stellenbosch University will not infringe any

third party rights and that I have not previously in its entirety or in part submitted it for obtaining any

qualification.

Date: 25 November 2013

Copyright © 2013 Stellenbosch University

All rights reserved

Stellenbosch University http://scholar.sun.ac.za

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SUMMARY

Modern consumers are health conscious and are shifting towards more naturally produced

products such as free range chicken. Commercial broiler strains are not suitable for free range

rearing and an alternative genotype is needed that will serve the South African market with the

acceptable meat quality as a broiler. The objective of this study was to investigate the effect of

production system (free range and intensive reared) and genotype (Broiler (COBB™), Ross 308 X

Potchefstroom Koekoek hybrid and Potchefstroom Koekoek) on chicken meat quality. This was

quantified on the morphological, physical (pH, colour, drip and cooking loss, water holding capacity

and tenderness), chemical composition (moisture, protein, fat, ash contents and fatty acid profile),

sensory quality and consumer preference of various chicken meat portions.

The results of this study indicate that genotype had a more pronounced effect than

production system on the morphological and growth properties of chicken meat, as well as on the

sensory characteristics and consumer preference. The broilers had the best (P ≤ 0.05) feed

conversion ratio (FCR), highest average daily gain (ADG) and European production efficiency

factor (EPEF), followed by the Hybrid and then the Potchefstroom Koekoek. For each genotype,

the free range chickens produced heavier (P ≤ 0.05) live weights than intensively reared chickens.

Despite the poorer growth performance and efficiency of the medium growing Hybrid birds, they

had less mortality and fewer leg disorders than the broiler. Additional to these factors, the Hybrid

Free Range had higher thigh, drumstick and wing yields (P ≤ 0.05) than the broiler. When

investigating the correlation between the chemical and sensory data, it was observed that the

Hybrid scored significantly higher (P ≤ 0.05) in both flavour and aroma than the Broiler and

Koekoek genotypes for both production systems.

For colour, pH and polyunsaturated to saturated fatty acid ratio (PUFA:SFA), the effect of

production system was more pronounced than the effect of genotype. Rearing chickens in a free

range environment increased the PUFA:SFA ratio (P ≤ 0.05), making it beneficial to human health.

Free range rearing resulted in lower muscle pHu (P ≤ 0.05), darker (L* value) (P ≤ 0.05), less red

and yellow (a* and b* value) (P ≤ 0.05) chicken meat. It also influenced the chemical composition

in different carcass portions; for example, a lower fat content in the thigh and higher protein in the

breast of the Broiler.

Correlation with the sensory results indicated that juiciness, tenderness, chicken aroma and

chicken flavour are the main drivers of liking for consumer’s preference towards chicken meat.

The consumers predominantly preferred the Hybrid (P ≤ 0.05) in a blind tasting session, but

when information was given on the production system of a chicken product, the consumers lean

more towards a free range reared product than an intensive reared product. This indicates that

consumer perception plays an immense role in consumer decision making. Cluster analysis was

also performed to ascertain whether the consumers differed in their degree of liking of the intrinsic

character of the respective chicken samples. Three different clusters of consumers were identified:


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1) Consumers that prefer free range reared chicken meat, 2) Consumers that prefer intensively

reared chicken meat, 3) Consumers that prefer both free range and intensive reared chicken meat.

In conclusion, the Hybrid seems to be a viable option for free range production systems in

South Africa, without negatively affecting the overall quality of the meat or consumer acceptance.


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OPSOMMING

Moderne verbruikers is baie meer gesonheidsbewus en verkies meer natuurlik geproduseerde

produkte soos vrylopende (free range) hoenders. Die kommersiële braaikuiken is nie geskik vir

vrylopende produksie nie en `n ander genotipe word benodig wat die Suid-Afrikaanse mark sal kan

voorsien met aanvaarbare vleiskwaliteit vergelykbaar met dié van die braaikuiken. Die doel van

hierdie navorsing was om die effek van produksiestelsel (vrylopend en intensief) en genotipe

(braaikuiken (COBB™), Potchefstroom Koekoek en Ross 308 X Potchefstroom Koekoek kruising)

op die morfologiese, fisiese (pH, kleur, drip- en kookverlies, waterhouvermoë en taaiheid),

chemiese samestelling (vog-, proteïen-, vet-, asinhoud en vetsuurprofiel), sensoriese kwaliteit en

verbruikersaanvaarbaarheid van verskeie hoender vleis porsies te bepaal.

Hierdie navorsing het getoon dat genotipe `n groter invloed gehad het as produksiestelsel

op die groei en morfologiese eienskappe van die hoenders, asook op die sensoriese eienskappe

en verbruikersaanvaarbaarheid. Die braaikuiken, gevolg deur die Ross X Koekoek kruising en dan

die Koekoek, het die beste (P ≤ 0.05) voeromsetverhouding (FCR), gemiddelde daaglikse toename

(GDT) en Europese produksie effektiwiteitsfaktor (EPEF) getoon. Vir elke genotipe het die

vrylopende hoenders swaarder (P ≤ 0.05) lewende massa by slag getoon. Ten spyte daarvan dat

die Ross X Koekoek kruising swakker groei en effektiwiteitsresultate getoon het, het hulle laer

mortaliteite en minder been breuke en beserings as die braaikuiken gehad. Die Ross X Koekoek

kruising wat vrylopend groot gemaak is, het ook swaarder dy, boud en vlerkie massa (P ≤ 0.05) as

die braaikuiken getoon.

Die navorsing het ook getoon dat kleur, pH en die poli-onversadigde tot versadigde vetsuur

verhouding (PUFA:SFA) meer beïnvloed is deur die effek van produksiestelsel as genotipe. Die

hoenders wat in ŉ vrylopende omgewing grootgemaak is se PUFA:SFA verhouding is hoër as dié

van intensiewe boerdery, wat dit voordelig maak vir menslike gesondheid. Vrylopende hoenders

se vleis is donkerder (L*) (P ≤ 0.05) en het ook laer rooi, geel (a* en b*) en pH (P ≤ 0.05) waardes

getoon. Produksiestelsel effek het ook variërende chemiese waardes in verskillende karkas

porsies tot gevolg gehad: ŉ laer vetinhoud is gevind in die dy en ŉ hoër proteïeninhoud in die

borsies van die braaikuikens wat vrylopend grootgemaak is.

Korrelasies met die sensoriese data het ook getoon dat sappigheid, taaiheid en

hoendervleis geur die grootste dryfvere is in verbruikersaanvaarbaarheid. Tydens die

verbruikerstoetse waar die verbruikers die gaar hoendervleis blind geproe het, het die verbruikers

oor die algemeen meer gehou van die Ross X Koekoek kruising in vergelyking met die ander

hoender genotipes (P ≤ 0.05), maar sodra inligting oor die verskillende produksiestelsels gegee is,

het die verbruikers aangedui dat hulle hoenders wat vrylopend groot gemaak is, verkies. Dit dui

daarop dat persepsies ŉ baie belangrike rol speel in die verbruiker se finale besluitnemingsproses.

Statistiese segmentasietegnieke is ook op die data uitgevoer ten einde te bepaal of verbruikers in

groepe verdeel kan word wat betref hul voorkeur van die sensoriese of intrinsieke eienskappe van

die hoenderprodukte. Drie verskillende groepe is geïdentifiseer, nl. verbruikers wat 1) vrylopende


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hoender vleis verkies; 2) intensiewe hoender vleis verkies; 3) beide vrylopende en intensiewe

hoender vleis verkies.

In die lig van bogenoemde resultate wil dit voorkom of kruisteling tussen die gewone

braaikuiken en die Potchefstroom Koekoek ŉ moontlike opsie is vir die Suid-Afrikaanse vryloop

hoenderbedryf. Hierdeur word daar van vrylopende produksie stelsels gebruik gemaak sonder om

die vleiskwaliteit of gebruikers aanvaarbaarheid negatief te beïnvloed.


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ACKNOWLEDGEMENTS I wish to express my sincerest appreciation and gratitude to the following individuals and

institutions, which made the completion of this thesis possible:

Prof L.C. Hoffman, your inspiration, patience, motivation, guidance, encouragement, time and

teaching me how to carpe diem. And all the Café G.O. 1 coffees. Dr. E. Pieterse, for your advice,

guidance and jokes, you always put a smile on my face!

M. Muller, you are a great inspiration to me, your organising skills are the best, thank you for all the

guidance, motivation and understanding.

Postgraduate students for all your help, late nights and early mornings, support and advice and all

the fun times we had together: Adina Bosch, Greta Geldenhuys, Coleen Leygonie, George

Lorenzen, Schutz Marais, Jeannine Neethling, Nikki Neethling, Katryn Schoon, Monlee

Swanepoel, Altie Burger and Maxine Jones.

Staff members at the Department of Animal Sciences, whether it was help in the form of guidance,

advice or physical work: Jannine Booyse, Micheal Mlambo, Adele Botha, Lindie Liebenberg,

Cherryl Muller, Gail Jordaan, Lisa Uys, Beverly Ellis, Danie Bekker.

Staff members of the Sensory laboratory at the Department of Food Science: Erica Moelich, John

Achilles and James Achilles. To everyone that tasted the chicken samples at the consumer panel

and everyone on the sensory trained panel.

Staff members at Mariendahl Experimental Farm.

Marieta van der Rijst and Prof. M. Kidd for statistical analysis, advice and patience.

OSP Food Security initiative for funding and The National Research Fund (NRF) for financial

support.

To all my close friends and family for their support, understanding and words of encouragement

throughout the project, whether it was over a cup of coffee, lunch, a glass of wine, mountain bike

ride or on top of a mountain.

Stiaan, for your endless patience, belief, encouragement, strength, support and love.

My parents, Giep and Cecile Joubert, for their love, continuous support, belief in my abilities, for

consistently praying for me and of course, their financial support.

To my Heavenly Father, for giving me the ability, strength, endurance and provision during this

time, and all of the time, which I do not deserve. All honour and glory to Him!


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LIST OF ABBREVIATIONS

µL Micro liters ADG Average daily gain AMEn Nitrogen-corrected apparent metabolizable energy value Anon. Anonymous ANOVA Analysis of variance ARC Agricultural Research Centre ATP Adenosine triphosphate BFR Broiler free range BI Broiler intensive DA Discriminant analysis DFD Dark, firm, dry meat DHA Docosahexaenoic fatty acid DPA Docosapentaenoic fatty acid EPA Eicosapentaenoic fatty acid EPEF European production efficiency factor FAME Extraction of the fatty acid methyl esters FAO Food and Agriculture Organisation FCR Feed conversion ratio FSA Food Standards Agency g Gram h Hour HFR Ross X Potchefstroom Koekoek hybrid free range HI Ross X Potchefstroom Koekoek hybrid intensive IMF Intramuscular fat KFR Potchefstroom Koekoek free range kg Kilogram KI Potchefstroom Koekoek intensive KN Kilo Newton L Liters LDL Low density lipoprotein LSD Least significant difference min Minuets MUFA Monounsaturated fatty acids N Newton n-3 Omega 3 fatty acid n-6 Omega 6 fatty acid n-6:n-3 Omega 6 to omega 3 ratio ND Non-detected PCA Principal Component Analysis pHu pH post mortem (ultimate pH) PSE Pale, soft, exudative meat PUFA Polyunsaturated fatty acids PUFA:SFA Polyunsaturated to saturated fatty acid ratio r Coefficient of variance s Seconds


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SAPA South African Poultry Association SD Standard deviation SFA Saturated fatty acids WBSF Warner bratzler shear force WHC Water holding capacity


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NOTES

This thesis is presented in the format prescribed by the Department of Food Science at

Stellenbosch University. The structure is in the form of one or more research chapters (papers

prepared for publication) and is prefaced by an introduction chapter with the study objectives,

followed by a literature review chapter and culminating with a chapter for elaborating a general

discussion and conclusion. Language, style and referencing format used are in accordance with

the requirements of the International Journal of Food Science and Technology. This thesis

represents a compilation of manuscripts where each chapter is an individual entity and some

repetition between chapters has, therefore, been unavoidable.

Results from this study have been presented at the following symposium:

Annual Congress of the South African Society for Animal Science (SASAS), 11 – 14 JULY 2011,

Stellenbosch, Western Province, South Africa.


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CONTENT DECLARATION ............................................................................................................................... i

SUMMARY ...................................................................................................................................... ii

OPSOMMING ................................................................................................................................. iv

ACKNOWLEDGEMENTS ............................................................................................................... vi

LIST OF ABBREVIATIONS ............................................................................................................ vii

NOTES ........................................................................................................................................... ix

CHAPTER 1: General Introduction ............................................................................................... 1

References .................................................................................................................................. 3

CHAPTER 2: Pilot study on the sensory profile of commercial available broilers marketed as intensively or free range reared ............................................................................ 5

References ................................................................................................................................ 14

CHAPTER 3: Literature review ................................................................................................... 17

Introduction ............................................................................................................................... 17

Consumer perception and preferences ...................................................................................... 20

Experimental units ..................................................................................................................... 24

Factors effecting meat quality .................................................................................................... 29

Effect of genotype and production system ................................................................................. 34

Conclusions ............................................................................................................................... 46

References ................................................................................................................................ 47

CHAPTER 4: Effect of rearing system on genotype on the growth, carcass and individual portion yield of chicken ..................................................................................... 58

References ................................................................................................................................ 73


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CHAPTER 5: The influence of rearing system and genotype on the physical and chemical characteristics of chicken meat ........................................................................ 76

References ................................................................................................................................ 98

CHAPTER 6: Effect of rearing system and genotype on the sensory, physical and chemical quality of chicken meat ................................................................................... 103

References .............................................................................................................................. 125

CHAPTER 7: A South African perception of chicken meat .................................................... 131

References .............................................................................................................................. 150

CHAPTER 8: General conlusions and recommendations ...................................................... 153

Addendum A ............................................................................................................................. 156


1

CHAPTER 1

GENERAL INTRODUCTION

Over the past decade poultry production has shown a rapid increase and currently dominates the

South African agricultural sector (FAO, 2012; Anon., 2012). This increase is ascribed to higher

consumer demand for poultry products and fluctuating red meat prices. In 2011, the total global

annual poultry meat production was approximately 101.6 million tonnes compared to 109.0 million

tonnes pork, 67.5 million tonnes beef and 13.5 million tonnes mutton (FAO, 2012). The average

South African person consumes approximately 66 kg of meat (combined species) annually, of

which 32.96 kg is poultry (Anon., 2012). In South Africa, poultry consumption is more than all the

other animal protein sources combined (Department of Agriculture, Forestry and Fisheries (DAFF),

2011).

Consumption of fresh meat and meat products are mainly driven by quality but also

influenced by meat prices and per capita income (Zhao & Schroeder, 2010). The recession and a

decrease in consumer income, has forced consumers to buy and consume cheaper sources of

protein such as poultry. In South Africa, chicken breasts/fillets are sold on the retail market for

32% of the price of beef loin steak and 70% of pork fillet. Also, consumers are price sensitive,

especially in developing countries and will thus tend to purchase products that are perceived to be

value for money.

Chicken meat is a low fat protein source and provides essential vitamins and minerals such

as niacin, vitamin A, vitamin E and magnesium. It also has a favourable ratio of polyunsaturated

fatty acids to saturated fatty acids (PUFA:SFA) making it beneficial to consumers within a

cholesterol lowering diet and thereby helping to reduce the risk of cardiovascular diseases

(Charlton et al., 2008). Consumers frequently see chicken meat as a “healthier” option when

compared to other meat or protein products on the market (Verbeke & Viane 1999; Charlton et al.,

2008 du Toit & Crafford, 2003).

The modern consumer is also more conscious of animal welfare and health; they request

products that are environmentally friendly, promote sustainability, have nutritional value, excellent

meat quality and that tastes good (Sundrum, 2001; Hoffman & Cawthorn, 2012). Studies on

consumer perception of chicken meat and different rearing systems revealed that consumers

believe that the meat of free range chickens is healthier and tastier than birds reared in intensive

production systems, making their overall perception positive towards free range production

systems (Verbeke & Viane 1999; Yeung & Morris, 2001; Harper & Makatouni 2002; Grunert et al,

2004; Greene et al., 2005 as cited by Fanatico et al., 2005a; Fanatico et al., 2007; Castellini et al.,

2008; Branciari et al., 2009). The question arises, however, if these beliefs are true about free

range chicken meat or whether it is just a marketing strategy to convince ill-informed consumers?

Also, how do South African consumers perceive the meat from extensively reared animals?


2

The three most important factors that should be taken into consideration with regard to the

nutritional information about fat in meat products is the total fat content, the polyunsaturated to

saturated fatty acid ratio (PUFA:SFA) and the omega 6 to omega 3 ratio (n-6:n-3) (Enser et al.,

1998; Enser, 1999). Free range reared chicken meat is considered to have less saturated fat

(SFA), higher polyunsaturated fat (PUFA) and a lower ratio of n-6:n-3 than intensive reared

chicken meat (Castellini et al., 2002; Jahan & Paterson, 2007).

Environment and activity level influences the muscle growth and fibre type composition of

birds and consequently affect the chemical composition and overall quality of the meat (Lawrie &

Ledward, 2006). Free range production systems would expose the birds to fluctuating

temperatures and increased exercise on the forage area (Fanatico et al., 2005b). Therefore it

would be expected that free range reared birds reach maturity slower (older in age at slaughter

weight) than intensive reared birds, resulting in a more intense flavour of the meat, since more fat

can be deposited for flavour development (Lawrie & Ledward, 2006; Elmore et al., 1999). The

muscles of free range birds will have had a higher level of physical activity, which will result in

tougher meat due to increased intramuscular collagen content (Smith & Carpender, 1970; Lewis et

al., 2005)

The future of free range agriculture will, to a large extent, depend on consumer demand. In

order for the free range chicken industry to expand their market share, they have to increase the

demand for chicken meat through developing convenient, innovative, healthy and high quality

products that appeal to the high income consumer.

Castellini et al. (2008) and Van de Weerd et al. (2009) reported that only slow-growing

chicken strains can completely benefit from an extensive rearing system and the fast growing

strains are considered slow to adapt to change. During the genetic selection for fast growing

animals, their behaviour has changed to reduced kinetic activity (Schütz & Jensen, 2001; Branciari

et al., 2009). Therefore, a slower growing chicken line is needed, that can adapt to the harsh

conditions of the South African weather, can eat the forage in an extensive production system (and

thus exercise more) and still give the same or better meat quality as the broiler. Numerous studies

have been done on production and genotype effects on chicken meat quality, but never before in a

South African free range environment with a South African indigenous chicken genotype.

The objective of this study was therefore to investigate the impact of production system

(free range and intensive reared) and genotype (Commercial Broiler, Ross 308 and Potchefstroom

Koekoek hybrid and Potchefstroom Koekoek) on the morphological, physical meat quality (pH,

colour, drip and cooking loss, water holding capacity and tenderness), chemical composition

(moisture, protein, fat, fatty acid profiles and ash contents), sensory quality and consumer

preference of chicken meat.


3

REFERENCES

Anonymous (2012). South African poultry association (SAPA) Industry profile. [WWW document].

URL http://www.sapoultry.co.za/information_industry profile.php. 10 October 2012.

Branciari, R., Mugnai, C., Mammoli, R., Miraglia, D., Ranucci, D., Dal Bosco, A. & Castellini, C.

(2009). Effect of genotype and rearing system on chicken behaviour and muscle fibre

characteristics. Journal of Animal Science, 87, 4109-4117.

Castellini C., Mugnai, C., Dal Bosco, A. (2002). Effect of organic production system on broiler

carcass and meat quality. Meat Science, 60, 219-225.

Castellini, C., Berri, C., Le Bihan-Duval., E. & Martino, G. (2008). Qualitative attributes and

consumer perception of organic and free-range poultry meat. World's Poultry Science

Journal, 64, 500-512.

Charlton, K.E., Probst, Y.C., Tapsell, L.C., Blackall, P.J. (2008). Food, Health and nutrition: Where

does the chicken fit?. Australian Chicken meat Federation. 1-19.

Department of Agriculture, Forestry and Fisheries (DAFF) (2011). Trends in the

Agriculturalsector.Government Printer, Pretoria, South Africa.

Du Toit, L. & Crafford, S. (2003). Beliefs and purchasing practices of Cape Town consumers

regarding organically produced food. Journal of Family Ecology and Consumer Sciences.

31, 1-11.

Elmore, J.S., Mottram, D.S., Enser, M. & Wood, J.D. (1999). Effects of the polyunsaturated fatty

acid composition of beef muscle on the profile of aroma volatiles. Journal of agricultural and

Food Chemistry. 47, 1619-1625.

Enser, M., Hallet, B., Fursey, G.A.., Wood, J.D. & Harrington, G. (1998). Fatty acid content and

composition of UK beef and lamb muscle in relation to production system and implication

for human nutrition. Meat Science, 43(3), 329-341.

Enser, M. (1999). Nutritional effects on meat flavour and stability. In: Poultry Meat Science. (edited

by R.I. Richardson, & G.C. Mead). Pp. 197–215. Wallingford, UK: CABI Publishing.

Fanatico, A.C., Cavitt, L.C., Pillai, P.B., Emmert, J.L., & Owens, C.M. (2005a). Evaluation of

slower-growing broiler genotypes grown with and without outdoor access: meat quality.

Poultry Science, 84, 1785-1790.

Fanatico, A.C., Pillai, P.B., Cavitt, L.C., Owens, C.M. & Emmert, J.L. (2005b) Evaluation of slower-

growing broiler genotypes grown with and without outdoor access: growth performance and

carcass yield. Poultry Science, 84, 1321-1327.

Fanatico, A.C., Pillai, P.B., Emmert, J.L., Gbur, E.E., Meullenet, J.F. & Owens, C.M. (2007).

Sensory attributes of slow- and fast-growing chicken genotypes raised indoors or with

outdoor access. Poultry Science, 86, 2441-2449.

FAO, (2012). .FAO Food Outlook [Internet document]. URL

http://www.fao.org/docrep/015/al989e/al989e00.pdf


http://www.sapoultry.co.za/information_industry%20profile.php.%2010%20October%202012


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Greene, D., Wenger, E., Alvarado, C., Thompson, L. & O’Keefe, S. (2005). Consumer perception

of meat quality and shelf-life in commercially raised broilers compared to organic free range

broilers. Abstract 158 in 2005 International Poultry Science Forum, Atlanta, GA. SPSS,

Tucker, GA. (Abstr.)

Grunert, K.G., Bredahl, L., Brunsø, K. (2004). Consumer perception of meat quality and

implications for product development in the meat sector - a review. Meat Science, 66, 259-

272.

Harper, G.C. & Makatouni, A (2002). Consumer perception of organic food production and farm

animal welfare. British Food Journal, 104, 287-299.

Hoffman, L. & Cawthorn, D. (2012). Consumer preferences in meat. In: Proceeding of the 2nd

International Seminar on Animal Industry. Pp. 9-22. July 2012 Jakarta, Indonesia.

Jahan, K. & Paterson, A. (2007). Lipid composition of retailed organic, free-range and conventional

chicken breasts. International Journal of Food Science and Technology, 42, 251–262.

Lawrie, R.A. & Ledward, D.A. (2006). Lawrie`s Meat Science, 7th ed. Cambridge, England:

Woodhead Publishing Limited.

Lewis P.K. Jr., Rakes, L.Y., Brown, C.J. & Noland, P.R. (2005). Effect of exercise and pre-

slaughter stress on pork muscle characteristics. Meat Science, 26, 121-129.

Schütz, K.E. & Jensen, P. (2001). Effects of resource allocation on behavioural strategies: a

comparison of red jungle fowl (Gallus gallus) and two domesticated breeds. Poultry

Ethology, 107, 753–765.

Smith, G. & Carpenter, Z. (1970). Lamb carcass quality. III. Chemical, physical and histological

measurements. Journal of Animal Science, 52, 453-459.

Sundrum, A. (2001). Organic livestock farming: A critical review. Livestock Production Science, 67,

207-215.

Van de Weerd, H.A., Keatinge, R. & Roderick, S. (2009). A review of key health-related welfare

issues in organic poultry production. World's Poultry Science Journal, 65, 649-684.

Verbeke, W. & Viane, J. (1999). Beliefs, attitude and behaviour towards fresh meat consumption in

Belgium; empirical evidence from a consumer survey. Food Quality and Preference, 10,

437-445.

Yeung, R.M.W & Morris, J. (2001). Consumer perception of food risk in chicken meat. Nutrition &

Food Science, 31 (6), 270-278.

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and options for the Asia-Pacific region. Natural Resources Forum, 34, 4-15.


5

CHAPTER 2

PILOT STUDY ON THE SENSORY PROFILE OF COMMERCIAL AVAILABLE BROILERS MARKETED AS INTENSIVELY OR FREE RANGE REARED

ABSTRACT

Modern consumers are more animal welfare conscious and as a result their interest in free range

poultry products is growing. The objective of this pilot study was to investigate the sensory

(flavour, aroma, toughness, mealiness, initial and sustained juiciness) and physical (drip loss,

cooking loss, water holding capacity) meat quality characteristics of chicken marketed as

conventional or free range in the South African market. The cooked pectolaris (breast) muscles of

commercially supplied conventional and free range chicken were compared by means of

descriptive sensory analysis. No significant differences (P > 0.05) were found for the attributes

chicken aroma, chicken flavour, metallic aroma, metallic aftertaste, initial juiciness and mealiness,

although the free range birds scored higher in sustained juiciness and were lower in toughness

(P ≤ 0.05) than the conventional birds. The two groups also differed significantly (P ≤ 0.05) from

each other with regard to percentage drip loss, percentage cooking loss and water holding

capacity. The major differences in this study can be ascribed to the higher tenderness and

juiciness of the free range sample. This study established that although commercially available

free range and conventional chicken breasts differ from each, the reasons for these differences are

not clear and thus external factors need to be controlled or standardised in further studies.

Keywords: Free range; Conventional; Sensory analysis; Chicken meat; Poultry

INTRODUCTION

The modern consumer is more conscious of animal welfare and as a result would like to purchase

products from animals that are extensively reared. Animal welfare can affect the quality of animal

products and has become a strategic marketing tool. Intensive production systems are being

criticised, by animal welfare organisations, for not providing adequate welfare to animals. This

disparagement has led to the development of poultry meat production under less intensive reared

conditions. Although consumers expect a higher degree of welfare in free range animals; this is

only true if slow-growing strains are used (Castellini et al., 2008). Furthermore, consumers believe

that the meat of free range chickens is healthier and tastier compared to those of birds reared in

confinement and their overall perspective is positive towards free range production systems

(Fanatico et al., 2007; Branciari et al., 2009). This consumer perception opens a market for more

naturally produced chicken products (Branciari et al., 2009). Although consumers indicate that


6

they are willing to pay premium prices for free range or organic products, this is not reflected in the

purchasing figures (Sundrum, 2001; IGD, 2007; Van Loo et al., 2011).

Research has shown improved welfare in chickens, i.e. better expression of natural

behaviour when having access to free range conditions than those in confined areas (Schütz &

Jensen, 2001; Branciari et al., 2009). In Europe, alternative poultry meat production i.e. free range

or organic, has gained wide recognition and resulted in branded products, such as the French label

“Rouge”, which has been very successful. Castellini et al. (2002) and Jahan et al. (2005) reported

that broiler birds exposed to more natural rearing conditions had increased activity which led to

lower lipid contents in the meat and this, combined with pasture intake, contributed to higher

consumer acceptability of the meat (Ponte et al., 2008).

Fast-growing chicken lines are inadequate in extensive management production systems

as several health and wellness problems occur, such as lameness, leg disorders and a high

mortality rate due to their excessive weight. However, they are still commonly used in extensive

conditions for economic reasons (Bokkers & Koene, 2003; Castellini & Mourvaki, 2007; Castellini

et al., 2008). Free-range production farmers in South Africa prefer to use the same fast-growing

meat chicken genotypes, i.e. ROSS, COBB, etc., used in intensive production systems, as the use

of slow-growing strains is not compulsory or economical. These fast-growing birds generally have

higher live weight and better carcass conformation, attributing to the widespread use of these

birds. Slower growing birds such as the indigenous Potchefstroom Koekoek, have greater leg and

lower breast yields than fast-growing birds of similar weight. Additionally, these birds show active

foraging behaviour which make them an ideal genotype for free range rearing. Poultry meat quality

is a complex phenomenon where the rearing system is but one of the non-genetic factors that can

significantly affect meat quality (Bogosavljević-Bosković et al., 2006). The main differences found

in literature regarding the assessment of the effect of unconventional production systems on

poultry meat quality, frequently are a result of birds from different age and genetic origins being

compared, rather than from the production system itself.

The growth of the free range chicken industry in South Africa will largely depend on

consumer demand. In order to expand this demand and market share the industry need to market

free range chicken meat through developing convenient, innovative, healthy and high quality

products that appeal to the high income consumer. The modern consumer wants quality meat, as

associated with the intensive meat broiler, but also demand products that are healthy,

environmentally friendly, promote sustainability and comply with animal welfare guidelines. These

complex and diverse aspects creates an enormous challenge for the industry. A possible solution

might be considering hybrids between native species (hardy) such as the Potchefstroom Koekoek,

with meat broilers (growth & quality).

Although various authors have considered the effect of rearing system and genotype on

meat quality, none have done research on the South African market (Castellini et al; 2002a;

Castellini et al; 2002b; Debut et al., 2003; Fanatico et al., 2005a; Fanatico et al., 2005b; Branciari


7

et al., 2009; Bogosavljević-Bosković et al., 2009; Fanatico et al., 2007b; Jaturasitha et al., 2008;

Abdullah et al., 2010; Poltowicz & Doktor; 2011). The aim of this exploratory study was to

investigate the sensory and physical meat quality attributes of chicken meat marketed as

conventional or as free range reared.

MATERIALS AND METHODS

Sampling

Twelve chicken breast fillets marketed as free range or conventional (intensive) were purchased

from a commercial outlet. It was assumed that the purchased samples were fed the same

commercial formulated diet as a telephonic discussion with the free range producer elicited the

response that they feed commercially available broiler diets. The experimental units included the

breast (M. pectolaris) muscles of the two treatments. Each treatment was replicated six times

(different breasts). The sensory analysis and physical measurements were performed on the

cooked right breasts. The analyses were thus performed on 12 (2 treatments x 6 replications)

birds.

Descriptive sensory analysis

The sensory analysis consisted of two meat treatments with six consecutive replications of the

sensory test, thus the total number of samples equals 12. The frozen breast samples from each

treatment, were removed from the freezer (-18°C) and defrosted in a refrigerator at 4°C for 12 h

prior to each sensory analysis session. The defrosted samples were removed from the packaging

and placed inside separate marked oven roasting bags (GLAD™, South Africa). The roasting bags

with the meat samples were then placed on a stainless steel grid and fitted on an oven roasting

pan Thermocouple probes, connected to a hand-held digital temperature monitor (Hanna

Instruments, South Africa) were inserted into the core of each of the meat samples where after, the

roasting bags were closed by a metal tie. The samples were placed in two conventional ovens

(Defy, model 835), pre-heated to 160°C and roasted until an internal temperature of 75°C was

recorded by the thermocouple probes (AMSA, 1995). The two conventional ovens were connected

to a computerised monitoring system which regulated the temperature of the ovens (Viljoen et al.,

2001). After the samples were removed from the oven and roasting bags, each sample were

allowed to cool down for 10-15 min and cut into 1 x 1 x 1 cm cubes. The meat cubes were

individually wrapped in aluminium foil squares and placed in glass ramekins (two cubes per

ramekin), each marked with a randomised three digit code. Before the samples were served to the

panellists for evaluation, the ramekins containing the meat samples were placed in a preheated

oven (100°C) and reheated for 10 min.


8

Descriptive sensory analysis was performed on the two meat treatments by a panel of nine

judges, each with previous experience in sensory analysis of meat. The panellists were trained in

descriptive sensory analysis of meat according to Lawless and Heymann (2010) and the guidelines

for sensory analysis of meat as described by the American Meat Science Association (AMSA,

1995). The panel received four training sessions. During each session the panellists received 1 x

1 x 1 cm cubes of meat from the four different meat treatments. The sensory attributes were

analysed using a 100 mm unstructured line scale with zero (equal to low intensity) on the left hand

side and 100 (equal to extreme intensity) on the right hand side (AMSA, 1995). Eight sensory

attributes were decided on by the panellists (Table 2.1). Panellists were seated at individual

sensory booths with artificial light in a temperature controlled (21°C) room, and were provided with

the four meat treatments, in a randomised order, with distilled water (21°C), half an apple and

water biscuits (CARR, UK) to clean and refresh their palate between each sample evaluation. The

samples were analysed by completing the questionnaire on Compusense® (Compusense, Guelph,

Canada) compiled during the training sessions.

Table 2.1 Attributes used in the sensory analysis of chicken

Sensory attribute Description Scale

Chicken aroma Intensity of the aroma associated with typical cooked chicken as soon as the foil is removed

0 = Extremely bland 100 = Extremely intense

Metallic aroma Intensity of the aroma associated with metallic as soon as the foil is removed


Initial juiciness Amount of fluid exuded on the cut surface when pressed between the thumb and forefinger

0 = Extremely dry 100 = Extremely juicy

Chicken flavour Intensity of the flavour associated with typical cooked chicken prior to swallowing


Metallic aftertaste Intensity of the flavour associated with metallic prior to swallowing


Toughness The impression of toughness perceived after the first 5 chews using the molar teeth.

0 = Extremely tender 100 = Extremely tough

Sustained juiciness Intensity of the juiciness where juiciness is associated with fluid perceivable while chewing

0 = Extremely dry 100 = Extremely juicy

Mealy / powdery / Crumbly texture

Extreme mealiness is associated with a powdery, dry sensation in the mouth

0 = not mealy 100 = Extremely mealy

Physical measurements

Drip loss

The weight (g) of the breast fillets were documented before being vacuum-packed and frozen (-

18°C) for approximately one week. After the breast meat was defrosted in a fridge (4°C) for 24 h,


9

it was removed from the packaging and blotted dry with tissue paper and weighed again (g). The

difference in the weight of each of the samples was calculated as the percentage drip loss.

Cooking loss

The total weight loss during cooking (cooking loss) of the four treatments for the six replications

was determined by using the method described by AMSA (1995). The breast muscle from each

treatment was weighed (g) and documented before cooking. After the cooking process, the meat

was removed from the cooking bag and allowed to cool down for approximately 10-15 min. Before

recording the final weight (g), the meat was blotted with paper towel to remove excess moisture.

The difference in the weight of each of the samples was calculated as the percentage cooking loss.

Water holding capacity

The water holding capacity was performed according to the method described by Trout (1988). A

cooked meat sample from each of the two treatments and six replications were used. The meat

was cut into small pieces and a 0.5 g piece was placed on top of a filter paper (Lased, Paper Filter,

grade 292, diameter 90 mm, part nr. FLAS3205090). The filter paper together with the meat

sample was then placed between two Perspex plates and a standard pressure of 588 N was

enforced on the plates for 60 s. A photograph was then taken of the filter paper showing the

expelled liquid and meat areas. Image J Software (Version, 1.36b, NIH Image) were used to

calculate the ratio between the liquid (outer) and meat (inner) purge area to indicate the water

holding capacity of the meat sample.

Statistical analysis of data

Experimentally the study consisted of a randomised block design with two treatments and six

replications per treatment. The trained panel consisted of ten judges and the two treatments were

evaluated for the six sensory attributes established during the training sessions. The model for the

experimental design is indicated by the following equation:

Yij = µ + βj + ti + εij

where µ is defined as the overall mean, βj is the effect of the block, ti is the effect of the treatment

and εij is the error associated with the effect of the block and treatment. Outliers in the data were

identified and removed before statistical analysis using ANOVA. T-tests were used to test for

significant differences between treatment means. Least significant differences (LSD) were

calculated at a 5% significance level. Results were defined as being significant at P ≤ 0.05 and not

significant at P > 0.05. Correlations were made between the sensory attributes, physical

characteristics and proximate composition by means of the Pearson`s correlation coefficient


10

(Snedecor & Cochran, 1980). SAS™ statistical software (Statistical Analysis System, Version, 9.2,

2006, SAS Institute Inc., CARY, NC, USA) was used for the analyses of variance (ANOVA). The

multivariate statistical analysis and Principal Component Analysis (PCA) were performed using XL

STAT statistical software (Version 2011; Addinsoft, New York, USA). Principal component

analysis (PCA) is used to ascertain the association between the sensory attributes, instrumental

attributes and treatments.

RESULTS

Sensory attributes

The sensory means and standard deviations (± SD) of the two different treatments are indicated in

Table 2.2. It is clear from Table 2.2 that the mean values indicate that the chicken aroma was

quite prominent in both samples although it did not differ between treatments (P > 0.05). No

differences (P > 0.05) were found when comparing the two treatments for metallic aroma, initial

juiciness, chicken aroma, metallic aftertaste and mealiness. The mean values for chicken flavour

were 50.86 and 48.40, indicating that this attribute was fairly strong but not as strong as chicken

aroma (> 64.00). The metallic aroma and aftertaste mean values were below 5, indicating that the

panel found this attribute to be extremely low and barely recognisable. The small range within

which the mean values fall, indicate that the samples were perceived to be very similar for all of

these sensory attributes.

Although the panel scored the free range sample higher for sustained juiciness than the

conventional sample (P ≤ 0.05), the mean values for this attribute were between 39.60 and 47.64,

indicating that the samples were perceived as being slightly dry.

With regard to toughness the panel established that the free range sample was significantly

(P ≤ 0.05) more tender than the conventional sample. Although differences were detected, the

mean values of < 20 for toughness indicate that the samples were perceived as being quite tender.


11

Table 2.2 Mean scores (± SD) of sensory attributes of two chicken meat samples marketed as

conventional and free range

Attributes Intensive Free Range LSD

Chicken Aroma 67.98a ± 9.69 64.18a ± 9.00 5.20

Metallic Aroma 1.97a ± 5.05 1.26a ± 3.19 2.12

Initial Juiciness 54.57a ± 15.67 58.33a ±15.10 5.31

Chicken Flavour 50.86a ± 9.19 48.40a ± 9.99 5.06

Sustained Juiciness 39.60b ± 11.59 47.64a ± 12.61 5.54

Metallic Aftertaste 4.11a ± 6.81 4.28a ± 7.61 4.47

Toughness 18.36a ± 15.57 11.07b ± 17.81 5.24

Mealiness 12.25a ± 7.13 8.69a ± 6.85 4.41

Standard Deviation (SD); Least Significant Difference (LSD) ab Values in the same row with different superscripts are significantly different (P ≤ 0.05) Means determined by an unstructured line scale (0 = low intensity, 100 = high intensity)

Physical attributes

The physical attributes measured included drip loss, cooking loss and water holding capacity

(WHC) of the breast muscle samples and their means and standard deviations (± SD) are

presented in Table 2.3. The free range sample showed the lowest (P ≤ 0.05) percentage drip loss

(mean value = 2.27), compared to the conventional sample (mean value = 7.71). The free range

sample was also found to have a significantly (P ≤ 0.05) lower percentage cooking loss when

compared to the conventional sample. During the WHC pressure test, the free range sample

showed the highest ratio (P ≤ 0.05), indicating that the highest amount of fluid was released from

the free range breast meat sample.

Table 2.3 Mean scores (± SD) for the physical characteristics of chicken meat samples marketed

as conventional and free range

Measurement Intensive Free Range LSD

% Drip loss 7.71a ± 1.63 2.27b ± 0.89 2.24

% Cooking loss 19.85a ± 5.21 12.12b ± 0.59 3.83

WHC 3.79b ± 0.09 4.17a ± 0.19 0.16

Standard Deviation (SD); Least Significant Difference (LSD) at P = 0.05 a-b Values in the same row with different superscripts are significantly different (P ≤ 0.05) Sensory scale values ranged from Low (0) to Extreme (100)

Correlations

A Principal Component Analysis (PCA) bi-plot of the sensory and instrumental data is depicted in

Fig. 2.1. The combination of the two factors F1 and F2 explained 62.38% of the total variance of

which F1 and F2 explained 18.84% and 43.54%, respectively. In this bi-plot there is a distinct

separation of the two samples by the F1 axes, establishing the free range sample on the left hand

side and the conventional sample on the right hand side. In this bi-plot it can be seen that the

commercial free range samples associated strongly with initial juiciness, sustained juiciness, as


12

well as WHC. On the other hand, the conventional sample associated strongly with the attributes

toughness, mealy, chicken aroma and flavour and percentage drip loss and percentage cooking

loss.

What is also indicated in Fig. 2.1, is that the sensory attributes of juiciness associates with

WHC on the left side of the PCA plot and that percentage cooking loss and percentage driploss

associate on the right side of the PCA plot. These results indicate that there is an underlying valid

structure in the sensory and instrumental results.

Figure 2.1 Principle Component Analysis of sensory attributes and instrumental attributes

combined for broiler breasts marketed as conventional or free range birds.

DISCUSSION

Many factors may have influenced the chicken meat quality in this study, but since juiciness and

tenderness were the main effects, these two will be discussed further.

Juiciness

Initial juiciness in meat is defined as the moisture released during mastication, whereas the

stimulation of saliva secretion due to the presence of intramuscular fat is defined as sustained

juiciness (Lawrie & Ledward, 2006). The free range sample scored significantly higher for

sustained juiciness (Table 2.2) compared to the other chicken samples, but not for initial juiciness.

This is also illustrated in the PCA bi-plot (Fig. 2.1) where the free range sample associate with

Control

Control

Control

Control

Control

Control

FreeRange FreeRange

FreeRange

FreeRange FreeRange

FreeRange ChickenAroma

MetallicAroma

InitialJuiciness

ChickenFlavour

MetallicAftertaste

Toughness

Sustained Juiciness

Mealy

%Driploss

%Cookingloss WHC

-5

-4

-3

-2

-1

0

1

2

3

-10 -8 -6 -4 -2 0 2 4 6 8 10

F2 (1

8.84

%)

F1 (43.54%)

Biplot (axes F1 and F2: 62.38%)


13

sustained and initial juiciness and the conventional sample are situated on the opposite side

indicating a lesser correlation to juiciness. The free range samples also had the lowest cooking

and drip loss percentages and showed the highest score for water holding capacity. All these

attributes would thus seem to indicate that commercially available free range chickens have a

higher water content, which is more strongly bound and which is released once pressure (during

chewing or during the WHC test) is applied. This study further indicates that the correlation

between initial juiciness and WHC is inconclusive, but there is a moderately positive correlation

between sustained juiciness and water holding capacity (WHC) (r = 0.587; P = 0.045). Water

holding capacity is representative of the amount of moisture present within the meat, following the

cooking process. Unfortunately no pH measurements were taken and no correlation could thus be

made between WHC and pH. Offer and Trinick (1983) concluded that the initial juiciness of meat is

positively correlated with the WHC of meat, which is determined by the ultimate pH of the muscle.

Intramuscular fat generally contributes to sustained juiciness; the higher the percentage fat present

in the meat, the more juicy the meat is perceived to be (Lawrie & Ledward, 2006). However, no

proximate analyses were done on the different meat treatments in this exploratory study and

therefore no correlations could be made between the different attributes measured and not

measured. This is an aspect that warrants further research. It can be argued that when the meat

was not juicy (dry), the meat was perceived to be mealier, this is illustrated in the strong negative

correlation between mealiness with initial juiciness (r = -0.557; P = 0.060) and sustained juiciness

(r = -0.792 P = 0.002) and sustained juiciness with drip loss (r = -0.725; P = 0.008) and cooking

loss (r = -0.680; P = 0.015).

Tenderness

Tenderness is the ease of shearing, cutting or grounding meat during mastication and consumption

(Gillespie, 1960; Forrest et al., 1975). The free range meat sample proved to have the lowest

toughness (highest tenderness) compared to the other treatment (Table 2.1, Fig. 2.1). According

to previous studies, free range meat samples are not as tender as, or no significant differences

were found, when compared to intensive reared meat (Castellini et al., 2002; Farmer et al., 1997;

Fanatico et al., 2007, Ponte et al., 2008; Wang et al., 2009; Połtowicz & Doktor, 2011). In this

study the free range sample scored significantly lower for toughness, this is contradictory to what is

found in literature and what is expected. We would have expected the free range to be less tender

due to increased intramuscular collagen, as the birds would have had a higher level of physical

activity (Lewis et al., 1005). It is not clear why the free range sample was so tender, we can only

speculate that ante mortem and post mortem factors may have had an effect.

There is a moderately negative correlation between sustained juiciness and toughness

(r = 0.505; P = 0.094). Typically, the drier the meat the tougher it is perceived to be (Davis et al.,

1979; Hawkins et al., 1987). Toughness was also positively correlated to percentage drip loss

(r = 0.787; P = 0.002). As the percentage drip loss increased, the sensory tenderness decreased.


14

A similar result was also found for juiciness. Again this confirms the link between tenderness and

juiciness (Davis et al., 1979; Hawkins et al., 1987). It can be argued that the more water present in

the piece of meat that the panel member analysed, the higher the dilution of the connective tissue

per volume of the meat. Therefore the less juicy the meat the higher the content of the connective

tissue per bite and the tougher the piece of meat is perceived to be.

CONCLUSIONS

The aim of this study was to perform an explorative descriptive sensory analysis in order to

determine the sensory and physical quality characteristics of two commercial chicken samples

marketed as conventional and free range to consumers in the South African market.

Commercially, in South Africa, the same fast growing chicken strains used for intensive rearing are

used for free range production. The results of this investigation indicate that although some

attributes did not differ as expected; the free range samples were very tender and had a high

juiciness score causing these two attributes to be the main driving force for this treatment to be

different from the conventional samples. No information regarding the two rearing systems or their

ante and post mortem handling were collected, but it can be assumed that other extrinsic and

intrinsic factors may have had an effect on the greater tenderness and juiciness of the free range

sample. This indicates that in further studies as many factors as possible need to be controlled or

standardised.

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17

CHAPTER 3

LITERATURE REVIEW

INTRODUCTION

General background

The domestic chicken (Gallus gallus domesticus) is generally accepted to have originated

from the Red Jungle Fowl (Gallus gallus). They were first domesticated by man about 2500 BC in

Southeast-Asia and arrived in Sub-Saharan Africa sometime before 850 AD (Crawford, 1990;

MacDonald, 1992; Mozdziak, 2004; Rose, 1997). Poultry was initially domesticated for religious,

cultural and entertainment reasons and only later thought of as a food source.

More than a century of intense poultry breeding has resulted in a large diversity between

the strains/genotypes of the poultry species. Crossing closely related poultry genotypes to

produce hybrid offspring has the potential to increase the diversity of poultry even further (Rose,

1997).

Intensive broiler chicken production methods were first developed in the 1950`s. At that

time poultry meat production was less than 10% of the world`s total meat output. Since then

poultry meat output has taken a greater share of the expanding world meat market and it

accounted for over 20% of total meat output by the mid 1980`s (Rose, 1997).

The commercial poultry industry of today is tremendously uniform in composition and

appearance. Tightly managed breeding, incubation, rearing and nutritional systems have created

a bird that have less phenotypic variation. This uniformity has allowed poultry processing plants to

advance into highly automated facilities with an efficiency that is unmatched by other livestock

processors (Owens et al., 2010).

Chicken meat is a low fat protein source and provides essential vitamins and minerals such

as niacin, vitamin A, vitamin E and magnesium. It also has a favourable ratio of polyunsaturated

fatty acids to saturated fatty acids (PUFA:SFA) making it beneficial to consumers as a cholesterol

lowering diet and thereby helping to reduce the risk of cardiovascular disease (Charlton et al.,

2008). Broiler meat is inexpensive when compared to other animal protein sources on the market

(Fig. 3.1) with a producer selling price of R13.5/kg of carcass weight (Anon., 2012a). In addition,

chicken meat is packed in convenient portions or sold as ready to eat products, making it easy to

prepare in numerous dishes and ways thereby making it a very versatile product and a

convenience for the lifestyle we live in. Chicken meat does not have any religious restriction

against its consumption, making it a suitable product for different religions (Charlton et al., 2008;

Jaturasitha et al., 2008). Consumers frequently consider chicken meat as the “healthy” option


18

when compared to other animal protein sources (Verbeke & Viane 1999; Charlton et al., 2008 du

Toit & Crafford, 2003).

Figure 3.1 Animal protein selling prices (Modified from Anon., 2012a).

Modern consumers are more sensitive to animal welfare issues and are health conscious

as pertaining to the food they consume. They want to be informed to make educated choices and

would like to contribute to lowering their carbon footprint by looking after the environment (Grunert

et al., 2004; Grunert, 2006; Napolitano et al, 2010). There is a higher demand by consumers for

more “naturally” or extensive and humanely reared meat that has been produced with minimal use

of additives and chemicals. Broilers, which are used for intensive production, are not suited for

extensive production systems, as there is a higher incidence of mortality, lameness and leg

disorders, but they do gain weight very fast and their meat is acceptable to the consumer (Branciari

et al., 2009). Indigenous chickens, such as the Potchefstroom Koekoek, are adapted to the harsh

conditions of extensive rearing; they can be produced without any supplementary feed and are

extremely tolerant of diseases (Muchenje et al., 2009. However, they tend to grow slowly and do

not have as good a feed conversion ratio (FCR) as commercial broilers. Therefore, the South

African industry requires a chicken line that can adapt to the harsh conditions of a free range

system, is relatively fast growing, has a high meat yield per bird and produces meat which is

acceptable to the consumer.

Background on South African poultry industry

The poultry industry comprises of three distinct, separate branches, namely, the broiler-, the egg-

and the hatchery industries. The South African Poultry Association (SAPA) represents both

commercial and non-commercial farmers within these three branches. Approximately 70% of the

total broiler production in South Africa is supplied by roughly 13 large producers, while several

Beef abattoir selling prices

class A2/A3 (R/kg)

Beef abattoir selling prices

class C2/C3 (R/kg)

Average pork prices all

classes (R/kg)

Egg producer price (average

of all sizes in R/kg)

Broiler producer prices total

realisation (R/kg)


19

small production units and the informal sector are responsible for the remaining 30% (DAFF,

2011a).

In South Africa the poultry industry has developed into a major business over the past sixty

years, with production still increasing each year (Anon, 2011a). The main factor that contributed to

this growth was the higher demand for poultry meat by the health conscious consumer, as it has

become the “healthier” choice of meat globally (Van Marle-Köster, 2001; Mozdziak, 2004).

Another factor that may also have had an effect is the inexpensive price of chicken compared to

other meats in the market. The poultry industry dominates the South African agricultural sector as

the main supplier (23%) of animal protein for human consumption (Anon., 2012b). Over the past

eleven years, the number of day old broiler chicks placed have increased by 44% (3.9% annually)

while the number of broilers slaughtered have increased by 45.3% (3.66% annually) due to

improved productivity (Anon., 2012b).

The gross farm income from poultry meat in 2010 was R22 940 billion and from eggs

R6 658 billion, combined the gross farm income for 2010 was R29 598 billion for the poultry

industry (DAFF, 2011a). In 2010 the poultry industry supplied South Africa with 1661 840 tonnes

of meat.

There has been an increase of 4.1% in total broiler production from 2009 to 2010 with an

average of 18.6 million broilers slaughtered each week (DAFF, 2011a). Even with this increase,

South Africa is not self-sufficient. In 2010, broiler imports increased with 17% from 2009 (Anon.,

2012b). During 2010, approximately 73% of poultry imports into South Africa originated from

Brazil, 14% from Argentina and 7% from Canada. Despite the fact that the South African broiler

industry is exposed to the global poultry meat industry, where it has to compete with frozen

products imported from countries with relatively low production costs, growth still occurs (DAFF,

2011a). It was estimated that broiler production would increase by 1.04% in 2011 and an increase

of 2.8% was forecasted for 2012 (Anon., 2012b).

Poultry consumption globally and in South Africa

Globally the average person consumes about 41.6 kg of meat a year, but in South Africa the

average person consumes approximately 66 kg per annum (FAO, 2012; Anon., 2012b). In 2010

the average per capita consumption of poultry meat in South Africa was 32.96 kg per person

compared to 17.77 kg beef, 8.48 kg eggs, 4.58 kg pork and 3.16 kg mutton and goat. There was

an increase of 15% in the consumption of broiler meat from 2009 to 2010 (Anon., 2012b). Thus in

South Africa, poultry consumption is more than all the other animal protein scores combined, and

when all the animal protein in 2010 is accounted for, poultry was the highest making up 57% of the

total consumption of meat (beef, mutton, pork and poultry) (DAFF, 2011a).

Local poultry production provided 84% of the total poultry consumed during 2010. For the

same year an estimated 16% of local consumption of poultry meat consisted of imports and this

resulted in a 1% increase from 2009 in total consumption (DAFF, 2011a; Anon., 2012b).


20

The growth of the free range chicken industry in South Africa will largely depend on

consumer demand. In order to expand this demand and market share, the industry needs to

market free range chicken meat through developing convenient, innovative, healthy and high

quality products that appeal to the high income consumer. The modern consumer wants quality

meat, as associated with the intensively reared broiler, but also demands products that are healthy,

environmentally friendly, sustainable and comply with animal welfare guidelines as perceived by

the consumer. These aspects create a great challenge for the industry. One of the alternatives is

to look at hybrids between indigenous genotypes (hardy) such as the Potchefstroom Koekoek, with

broilers (growth and quality).

CONSUMER PERCEPTION AND PREFERENCES

Consumers perceive meat quality as multidimensional with the main dimensions being sensory

quality, ‘healthiness’, convenience, animal welfare and extensive production systems. At the point

of purchase, these qualities are often unknown to the consumer, and are therefore contingent

based on the information available (Grunert et al., 2004). A consumer attitude study towards fresh

meat (beef, pork and poultry) was conducted by Verbeke and Viane (1999). It was found that the

top five attributes in a descending order towards meat were quality, taste, freshness, hormone

absence and perceived ‘healthiness’. Poultry scored the highest in these attributes and is inclined

to be perceived more favourably than beef or pork. The only attribute that was scored lower than

beef and pork in poultry was the perception on ‘animal friendly’ (Verbeke & Viane, 1999)

Grunert et al. (2004) tested whether perception plays a role in consumer decision making

and evaluated further whether expectation was met by the actual experienced quality of

extensively produced meat. From Fig. 3.2 it can be seen that perceived quality (including taste

and tenderness) fell short of expectations after consumers consumed extensively produced pork

meat. The study clearly showed that extensive products may be wrongly classified if certain

qualitative characteristics, which are currently unfamiliar to consumers, are taken into account

(Grunert et al., 2004). Preferences are related to what consumers are familiar with and long term

exposure to intensive broiler meat flavour may cause resistance in the perception of other flavours.

This may be the reason why the taste attribute fell short of what the consumers were expecting

(Castellini et al., 2008). Castellini et al. (2008) also reported that an untrained consumer panel is

unable to distinguish in preference, appearance, texture and flavour between extensively and

intensively produced meat.


21

Figure 3.2 The difference between expected and experienced quality by consumers as pertaining

to the meat derived free range pork. (Modified from Grunert et al., 2004)

Diet / Health relationships

Over the past few decades consumers have become more health conscious and they prefer meat

that is leaner and has less visible fat. Chicken is generally recognised as a low fat, protein rich

meat source containing essential vitamins and minerals. The breast meat, in particular, is seen as

being low in fat, with a favourable profile of PUFA:SFA (Chalton et al., 2008). This is why

consumers perceive chicken meat as a healthier option in comparison to other protein sources.

Consumers also perceive free range and organic products to be healthier than intensive products

and an investment in their health (Verbeke & Viane 1999, Grunert et al, 2004). According to

various health establishments, the ratio of omega 3 to omega 6 (n-6:n-3) in meat should be less

than 4 and the PUFA:SFA should be greater than 0.45, to promote health and reduce the risk of

cardiovascular diseases (Enser, 1999, Wood et al., 2003, Warriss, 2010). Free range chicken

meat is considered to have less saturated fat (SFA), higher polyunsaturated fat (PUFA) and a

lower ratio of n-6:n-3 than intensive chicken meat making it a favourable health option (Castellini et

al., 2002a; Jahan & Paterson, 2007). However, the higher PUFA concentration makes the meat

more prone to rancidity and causes off-flavours to develop, but free range meat is also known to

have more vitamin E which helps maintain lipid stability (Valenzuela, 1995; Enser, 1999; Williams,

2000; Bou et al., 2004).

It is possible to change the fatty acid and nutrient composition of chicken meat by

manipulating the feed. For example, dietary supplements such as, omega 3 (n-3) fatty acids and

dehydrated alfalfa have been used to change the fat and cholesterol content of poultry meat

(Enser, 1999). The fatty acid profile of chicken can be changed by increasing the n-3 fatty acid

content by feeding chickens either linseed, rapeseed, soybean, fish extract or algae oils (Enser,

1999; Farmer, 1999).

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Overall Tender Taste Juicy Lean Health

Difference between expected and experienced quality


22

Animal welfare

In recent years consumers have become more concerned about the way animals are being

managed during farming, especially intensive production systems. Consumers request that animal

production farmers follow the animal welfare guidelines that contain Webster’s five freedoms and

state that they are willing to pay higher prices for certified humane products (Thompson, 1998; du

Toit & Crafford, 2003; Napolitano et al., 2010; Van Loo et al., 2011; Janssen & Hamm, 2012).

Producers are worried about the growing demand for animal friendly products, since these

production systems increase production costs, and although consumers stated that they are willing

to pay premium prices for these products, this is frequently not reflected in the purchasing figures

(Sundrum, 2001; IGD, 2007, Van Loo et al., 2011). The five freedoms to ensure adequate animal

welfare as listed by the Farm Animal Welfare Council in 1993 are:

1. Freedom from thirst, hunger and malnutrition by ready access to fresh water and a diet to

maintain full health and vigour.

2. Freedom from discomfort by providing a suitable environment, including shelter and a

comfortable resting area.

3. Freedom from pain, injury, and disease by prevention or rapid diagnosis and treatment.

4. Freedom to express normal behaviour by providing sufficient space, proper facilities, and

company of the animal’s own kind.

5. Freedom from fear and distress by ensuring conditions that avoid mental suffering.

Of these five guidelines, it is especially the freedom to express natural behaviour and the

freedom from pain, injury and disease that have been questioned by animal welfare groups when

referring to intensive poultry production systems (Gade, 2002). Animal welfare groups argue that

when birds are reared in a confined environment; lameness and leg disorders may occur, because

the developing legs cannot support the increased body weight of the fast growing birds. The

added weight also places stress on their heart and lungs and a disorder called ascites can develop

(Gade, 2002; Branciari et al., 2009). Genetic selection for rapid growth rates and high productivity

in conventional systems has led to the worsening of animal health (Van de Weerd et al., 2009).

Meat quality

In intensive production systems, animals are being reared in total confinement and fed until they

reach the desired slaughter weight. This kind of environment is perceived to be “unnatural” by

consumers for animals cannot express natural behaviour. Therefore they do not associate

intensive production systems with good meat quality (Gade, 2002; Fanatico et al., 2007b; Van de

Weerd et al., 2009).

In both intensive and extensive production systems, there are welfare advantages and

disadvantages that may affect the meat quality positively or negatively. In extensive production

systems, animals may show more natural behaviour, but they may be more susceptible to stress

during the catching method, which affect the meat quality negatively, since they are not used to


23

human handling. Although intensive production systems may restrict natural behaviour, it is easier

to control the environment, feeding, diseases and treat individual animals. When natural behaviour

is restricted, animals may become aggressive and show dominance disorders, causing the animals

to fight which results in bruising and this may affect meat quality negatively. When intensive

systems are managed correctly, they can actually be better, from a welfare point of view, than

poorly managed extensive systems (Gade, 2002; Hoffman et al., 2004; Van de Weerd et al., 2009).

Environmental impact

Consumers are becoming more aware of their own environmental footprint and demand products

that are more environmental friendly. Chicken meat is considered the “green” meat, because it

uses the least energy of all the livestock production systems and has the lowest impact in terms of

its potential contribution to global warming (Anon., 2006; Charlton et al., 2008; Nunes, 2011).

Agriculture generates 15.6% of the world’s total greenhouse gasses annually, with the main

contributors being beef cattle, sheep and dairy cattle. Poultry contributes as little as 1%

greenhouse gasses annually (Anon., 2006). The reasons why the broiler production systems

contribute so little to global warming are: it has a short growing cycle, it is land usage efficient

needing only 20 to 40 m2 to produce 1 kg of meat and to produce this 1 kg of meat, less than 2 kg

feed and 3.9 L of water is required (Nunes, 2011).

With regard to extensive production systems, where less energy is typically used for other

food products, in the case of chickens the opposite is true. However, extensive chicken production

systems still have a lower environmental impact than that of other livestock (Anon., 2006).

Food safety

Food safety is one of the key drivers when it comes to consumer preference towards free range or

organic foods. A chain of food scares over the past years, such as chicken meat contaminated

with salmonella and campylobacter and overuse of antibiotics in chicken increase concerns about

the consumption of chicken (Yeung & Morris, 2001a; Bailey & Cosby, 2005). A survey by the Food

Standards Agency (FSA) stated that 54% of all consumers are concerned about the hygiene status

of intensively reared raw chicken meat (FSA, 2011). Three main types of food risks related to

chicken have been identified, namely, microbiological risk, chemical risk and technological risk

(Yeung & Morris, 2001a).

Microbial risk refers to risk caused by microorganisms such as Salmonella and

Campylobacter, which cause food spoilage and food poisoning. Food borne illnesses may occur

through inadequate waste management, because animal diseases spread rapidly through faecal

contamination (Yeung & Morris, 2001b; Elamin, 2007). Chemical risk includes residues in food

due to antibiotics fed to chickens as well as the leftovers of agricultural chemicals in the animal

feed eaten. Continued use of antibiotics may result in the development of multidrug resistant

strains of pathogenic bacteria. Technical risk refers to the possible negative consequences of


24

technological advancements in food products such as genetic modification of foods (Yeung &

Morris, 2001b).

The Food and Agriculture Organisation (FAO) warned that in intensive production, where

animals are reared in confined unsanitary conditions, and there is no adequate waste management

system being applied, that this can cause a risk to meat safety. However, Gade (2002) states that

microbial risks can be reduced with good management practices. During periods of food safety

concern, consumer risk perception plays a key role as it greatly affects the purchase and

consumption behaviour of the consumer (Yeung & Morris, 2001b; Grunert, 2005).

EXPERIMENTAL UNITS

Muscle types

Muscles can be classified as light and dark in colour. As food they are referred to as the white

meat and the dark (red) meat (Parkhurst & Mountney, 1988). There are three types of muscle

fibres (type I, type IIa and type IIb) and muscles contain all three, although in some cases one type

can dominate (Parkhurst & Mountney, 1988; Mckee, 2003; Taylor, 2004). Table 3.1 shows the

relationship between fibre type and meat quality.

Table 3.1 Relationship between fibre type and meat quality (adapted from Taylor, 2004)

Fibre type Property Role in meat quality

I Red, oxidative, slow contracting, myosin type, more myoglobin, rich in mitochondria

High fat content, small fibre diameter, red colour, low glycolytic potential

IIa Red, intermediate, fast contraction, anaerobic Intermediate, faster into rigor than type I

IIb White glycolytic, fast contraction, rich in glycogen, anaerobic, fewer mitochondria

Largest fibres so toughest, pale colour, changes size with exercise regimes and age, high glycolytic potential so low pH

Type I, slow oxidative or red fibres are used for activities such as maintaining posture,

running and walking (Parkhurst & Mountney, 1988). They are rich in lipid, mitochondria, myoglobin,

red in colour and small in size. These fibre types are associated with the sensory characteristics

juiciness and flavour (Mckee, 2003; Taylor, 2004). Type II, fast glycolytic or white fibres are larger

in size, white in colour, have less myoglobin, less mitochondria and higher glycogen content than

type I (Mckee, 2003; Taylor, 2004). In a muscle, the fibre number is fixed at birth and with growth

and development the size and type changes. Muscles have a characteristic fibre type profile that

is species specific and related to the function of the muscle, other than exercise there are few

factors that change fibre type. Therefore the differences in muscle function will determine the

types of fibres present (Taylor, 2004).


25

Faster growing chicken lines were found to be more tender than slower growing chicken

lines, because of smaller fibre diameter. The latter increases with age, but these fibres do not

develop and become apparent as in those muscles with bigger fibres (Lawrie & Ledward, 2006;

Fanatico et al., 2005a). According to Taylor (2004), the differences in fibre type are usually greater

within genotypes. Domestication of animals have resulted in more larger type IIb fibres, thereby

increasing the meat toughness and also the colour, although some evidence shows that production

system has no effect on tenderness (Taylor, 2004; Castellini et al., 2008). When animals exercise

more, type IIa fibres are formed, therefore free range animals will have more red meat than

intensive reared animals (Fletcher, 1999; Taylor, 2004).

Breast

The breast portion consists of two muscles, the M. supracoracoideus and the M. pectoralis (Raj,

1999; Swatland, 2000). These two muscles are positioned in the front breast area of the carcass

where the sternum provides a surface for these muscles to attach onto. The breast portion of

chicken is usually sold with the muscle removed from the sternum as a deboned portion or as a

whole breast with the sternum still intact. The pectolaris muscle extends from the clavicle and the

coracoclavicular membrane to the pectoral crest of the humerus bone and is responsible for the

depression or downwards stroke of the wings during flight. This muscle is the largest body muscle

in the chicken, comprising about 8% of the total body weight. The supracoracoideus muscle

originates from the keel bone, on the dorsal side of the humerus bone, and is responsible for the

elevation or upwards stroke of the wings during flight (Raj, 1999; Swatland, 2000; Biewener, 2011).

Chickens are capable of fast flapping flights in which a thrust is created during depression of the

wings; therefore the pectoralis muscle is larger than the supracoracoideus muscle in chickens (Raj,

1999; Swatland, 2000). Both the pectoralis and supracoracoideus muscles consist of

predominantly (> 90%) white, type IIb, fast glycolytic fibres and only a small amount of red, type

IIa, fast oxidative glycolytic fibres (Ensminger, 1992; Chiang et al.,1995; Taylor, 2004; Branciari et

al., 2009). The breast, also known as the “white” meat of the chicken appears “white” in colour,

because of less myoglobin and fewer capillaries supplying blood to the muscle, and has a very

bland flavour and is not that juicy (McKee, 2003; Taylor, 2004).

The pectoralis major and pectoralis minor muscles are used during flight, therefore these

muscles will theoretically be more active (more type IIa fibre types and darker in colour) in an

extensive production system compared to animals in an intensive production system (Swatland,

2000).

Leg

The leg consists of two portions; the upper thigh and the lower drumstick and is often referred to as

the “dark meat”. All of the muscles found in the pelvic limb of galliform birds are listed in Table 3.1

and illustrated in Figures 3.3 and 3.4. The leg muscles are locomotive muscles which are used


26

during activities such as walking, grazing and running, therefore these muscles will be more active

in animals reared in an extensive production system compared to animals in an intensive

production system (Castellini et al., 2002a). These muscles consist of a combination of type I, type

IIa and type IIb fibre types, depending on the muscle.

The thigh is the upper part of the leg containing the femur and comprises of the muscles

biceps femoris, tendor fascia, semimembranosus and semitendinosus (Koch, 1973; Owens et al.,

2010). This portion is separated from the drumstick at the knee joint and removed from the

carcass at the hip joint (Swatland, 2000).

The drumstick is the lower part of the leg containing the tibia and fibula bones. This portion

is separated from the thigh at the knee joint between the femur and the tibia (Swatland, 2000;

Owens et al., 2010). The two main muscles of the drumstick are the peroneus longus and

gastrocnemius (Koch, 1973; Swatland, 2000; Owens, et al., 2010).


27

Table 3.2 The muscles of the pelvic limb in galliform birds as shown in Figures 3.3 and 3.4.

(Hudson et al., 1959)

Muscle name Abbreviation (from Fig. 3.3 & 3.4)

Thigh

M. adductor longus et brevis Add. Long.

M. ambiens Ambiens.

M. biceps femoris Bis. fem.

M. femoritibialisinternus Fem. tib. int.

M. femoritibialismedius Fem. tib. med.

M. glutaeusmedius et minimus Glut. med. et min.

M. iliotrochantericus anterior II troc. ant.

M. iliotrochantericusmedius II troc. med.

M. iliotrochantericus posterior II troc. post.

M. iliotibialis Il. tib.

M. iliacus Iliacus

M. ischiofemoralis Isch. fem.

M. obturatorexternus Obt. ext.

M. obturatorinternus Obt. Int.

M. piriformis Pirif.

M. sartorius Sar

M. semimembranosus Semin.

M. semitendinosus Semit.

Drumstick

M. extensor digitorumlongus Ext. dig. 1.

M flexor Digitorumlongus F. dig. 1.

M. flexor hallucislongus F. hal. 1.

M. flexor perforans et perforatusdigi II F. p et p. d. II

M. flexor perforans et perforatusdigi III F. p et p. d. III

M. flexor perforatusdigi II Flex. per. d II

M. flexor perforatusdigi II Flex. per. d III

M. flexor perforatusdigi IV Flex. per. d IV

M. gastrocnemius Gas.

M. peronaeusbrevis Per. brev.

M. peronaeuslongus Per. long

M. plantaris Plan.

M. tibialis anterior Tib. ant.


28

Figure 3.3 The superficial layer muscles of the pelvic limb in galliform birds, medial view. (Modified

from Hudson et al. 1959, the full names of the muscles are depicted in Table 3.2)

Figure 3.4 The superficial layer muscles of the pelvic limp in galliform birds, lateral view. (Modified

from Hudson et al. 1959, the full names of the muscles are depicted in Table 3.2)


29

FACTORS EFFECTING MEAT QUALITY

The major factors that can influence chicken meat quality are the genotype of chicken used, type of

production system in which it was reared, feed and season (Bianchi et al., 2007; Fanatico et al.,

2007a; Ponte et al., 2008),

Production system (Intensive, Free Range, Organic) and season

In South Africa there is no legislation with regard to free range and organic chicken farming, but

according to the SAPA`s code of practice (Anon., 2012c) and the European Regulation 2092/91,

1809/99 the minimum standards for intensive, free range and organic poultry production are listed

in Table 3.3.

In an intensive production system animals are housed in a confined and controlled (light,

temperature and ventilation) environment provided with water and a special formulated feed with

limited physical activity. Antibiotics and growth promoters may be given to these chicks. All these

practices still adhere to the code of practice for welfare of animals (Anon., 2012c). The

implementation of an intensive production system benefits the farmer with efficiency, high

productivity, high yields, high turn-over time, low production costs, high profit, low risk and minimal

land required (Notter et al., 1991). For intensive production systems, fast-growing chickens such

as broilers are generally used (Castellini & Mourvaki, 2007).

Free range chicken meat is produced using similar management, housing and feeding

practices as intensively produced meat chickens. The major differences are that free range

chickens are allowed access to an outside forage area for a minimum of six hours each day after

the brooding period and have a lower stocking density range. Free range production systems, limit

or avoid the use of chemical feed additives and genetic modified organisms in feed ingredients.

Antibiotics can be given to treat sick birds, but once treated; the meat from these birds cannot be

sold as free range (Anon., 2012c). The meat quality of free-range birds varies greatly since

producers use a wide range of slaughter ages, genotype types, feed ingredients and variation

within a rearing system (Castellini et al., 2008).

An organic production system, on the other hand, is where chickens are allowed to roam

outside during the day without any boundaries. These chickens are also reared under strict

farming standards adhered to for all stages of the animal’s Iife, being fed a mainly organic diet and

receiving no growth promoting chemicals or antibiotics. The minimum age at slaughtering is 81

days, since slower growing birds are normally used which take longer to reach slaughter weight

(Anon., 2012c).


30

Table 3.3 Comparison of the minimum standards between the three rearing systems, intensive,

free range and organic (Modified from Anon., 2012c)

Chicken meat sold as Intensive Free Range Organic

Kept in cages Yes/No No No

Housed in large barns Yes Yes Yes

Access to outdoor forage area No

Yes. Yes.

Required after 21 days of age

Required after 10 days of age (explicit requirement

regarding access to green vegetation) 6h per day

Stocking Density Maximum (inside the barns) 14-20 birds/m2 8-16 birds/m2

5 birds/m2 Depending on ventilation Depending on ventilation

Age of birds at slaughter 35 days 35 – 55 days 65 – 81 days

Given growth hormones No No No

May be given antibiotics for prophylactic and therapeutic purposes Yes No No

Feed consists mainly of grains Yes Yes Yes

Feed may contain supplements such as vitamins and amino acids Yes Yes Yes

Feed has to come from organic production (no chemical fertilizers, pesticides and herbicides used)

No No Yes

Use of GM products in feed Yes, to a limit Yes, to a limit No

Model Code of Practice for the Welfare of Animals applies Yes Yes Yes

Genetic Modified (GM)

Outdoor production systems have many factors such as temperature, photoperiod, and light

intensity, which are season dependant and not controlled. These factors may have an effect on

the performance of chickens grown extensively (Fanatico et al., 2005b). Gordon and Charles

(2002) reported that in colder temperatures and longer photoperiods, the feed intake of chickens

increases, and in warm temperatures it decreases, affecting the growth performance of these

birds. Consequently, differences in temperature and photoperiod can make reaching market

weight more difficult and may cause variation in the carcass quality of outdoor birds (Fanatico et

al., 2005b).

There are still a number of misconceptions about “free range” and “organic” and these

terms are often used loosely by all kinds of meat producers. These misconceptions are

exacerbated in countries where there are no guidelines or regulations pertaining to these

definitions.


31

Feed

The main difference between ruminants and chicken (monogastric) adipose tissue is chickens

have a low capacity for fatty acid and triglycerides synthesis and an undeveloped lymphatic

system. Therefore dietary lipids are directly incorporated into the tissue lipids, without any

modification (Wood & Enser, 1997; Fébel et al., 2008). Several experiments have been conducted

on chickens with different feed formulations e.g. soybean, linseed, fish oil, fishmeal, rapeseed to

only name a few. This is primarily done to change the nutritional (mostly fatty acid) composition of

chicken meat as well as change the efficiency of their growth rate (Enser, 1999).

Excessive amounts of n-6 PUFA and a very high n-6:n-3 ratio is found in today’s Western

diets that potentially enhance the probability of getting sick with diseases such as cancer,

inflammatory and autoimmune disease and various cardio vascular diseases (Simopoulos, 2002;

Gebauer et al., 2006). It is recommended that the ratio of n-6:n-3 in the human diet should be less

than 4 (Enser, 1999; Simopoulos, 2002; Wood et al., 2003). Western diets are therefore deficient

in n-3 PUFA (Simopoulos, 2002; Gebauer et al., 2006).

Numerous studies have shown that manipulating the dietary fatty acids of chicken feed

increases the n-3 PUFA in poultry meat. Linoleic acid (C18:2n6) and α- linoleic acid (C 18:3n3)

are two essential fatty acids needed for the synthesis of unsaturated eicosapentaenoic (EPA,

20:5n3) and docosahexaenoic acid (DHA, 22:6n3) and must be obtained from the feed (Nam et al,

1997; Enser, 1999; Wood et al., 2003). EPA and DHA can be directly incorporated into feed as

fish oil or as fish meal to raise the n-3 PUFA concentrations (Enser, 1999). The latter can also be

achieved by adding α-linolenicin (n-3 PUFA), of which rapeseed, soybean and linseed are sources,

to the feed and depending on the bird to synthesize and deposit the long chain fatty acids (Nam et

al, 1997; Enser, 1999). Adding α-linolenic acid to the feed can be advantageous since some of the

α-linolenic is directly deposited into the tissues of the bird. This lowers the n-6:n-3 to a more

favourable ratio in the human diet and consequently increases the EPA and DHA synthesis in

humans. It has been shown that linseed or linseed oil is much more effective than other oils in

raising the n-3 PUFA in broilers (Nam et al; 1997; Enser, 1999; Williams, 2000; Wood et al., 2003).

While the supplementation of feed with α-linolenic may increase the EPA and DHA concentrations,

the unsaturated fatty acids also increases the susceptibility of the lipid to oxidation, unless the feed

is also enriched with Vitamin E for oxidative stability (Valenzuela, 1995; Nam et al, 1997 Enser,

1999).

Feeding of fish oils or fish meal containing EPA and DHA however, results in a fishy taint in

the meat and after some studies it is established that fishmeal or oil should not exceed 12% of the

total feed formulation to avoid fishy taints. The difference in chicken flavour is dependent on which

fatty acid (α-linolenic or linolenic) is more abundant, α-linolenic acid produces a strong flavour and

linolenic acid produces a milder flavour (Enser, 1999; Wood et al., 2003).

Fébel et al. (2008), Coetzee and Hoffman (2001) and Coetzee and Hoffman (2002) reported

that chickens fed different diets reflected the same fatty acid pattern in the muscle tissues than in


32

the diets. The meat of birds fed sunflower and soybean oil in the diet, were enriched with PUFA of

which the majority consisted of linoleic acid (C18:2n6), and a significant increase in C18:2 were

observed in the meat. The birds fed linseed oil (n-3 fatty acid rich) showed a significant

incorporation of EPA and DHA and reduction of arachidonic acid (C20:4) in the muscle tissue.

Genotype

In South Africa there are many different types of chicken genotypes, whether slow or fast growing.

In this section only a few South African genotypes will be discussed.

The Potchefstroom Koekoek (Fig. 3.5b), a cross genotype between the Black Australorp

male and the White Leghorn female, was bred in the 1950`s at the Potchefstroom Agricultural

College of South-Africa by Mr. Chris Marais and was accepted as a South-African genotype by the

SAPA in 1976 (Ramsey et al., 2000). According to Fourie et al. (2006), the Koekoek was

specifically developed to adapt to the harsh free-range conditions (heat and cold; wet and drought,

sheltered in cages or unsheltered outside) of South-Africa. This was before modern commercial

chicken lines were industrialised and the Koekoek functioned as a dual purpose bird to provide the

industry with meat and eggs. The name Koekoek describes the black and white barred pattern of

the bird, rather than the genotype. This colouring is gender linked making it very useful in breeding

programs to tell males and females apart at a very young age (van Marle-Köster, 2001). The

Koekoek has a high average body mass in comparison to other South African indigenous

genotypes (Table 3.4) but it is slow growing. Birds only reach sexual maturity in 130 days and are

slaughter ready in 140 days (20 weeks) (Fourie et al., 2006).

Table 3.4 Average weights in grams of different indigenous South African chicken lines on 16 and

20 weeks (Adapted from van Marle-Köster & Webb, 2000)

16 weeks 20 weeks

Genotype Male Female Male Female

Koekoek 1839.0 1380.9 2381.1 1733.7

Ovambo 1742.4 1323.6 2167.3 1543.6

Venda 1569.6 1236.8 2015.2 1445.8

Naked neck 1521.7 1101.8 1950.0 1398.9


33

Figure 3.5 (a) a broiler (COBB500™) hen (b) a Potchefstroom Koekoek hen (c) an Ovambo

rooster (adapted from Anon., 2010a) (d) Venda hen and rooster (adapted from Anon.,

2010a) (e) Naked neck rooster and hens (adapted from ARC, 2010).

Broilers were first developed by the United States Department of Agriculture from a cross

between the Cornish male and the Playmouth White Rock female in the late 1940`s. A hybrid

variety of the latter was produced and through selective breeding the modern broiler was

developed by breeders (Rose, 1997; Mozdziak, 2004; Anon., 2010b). Broilers (Fig 3.5a) are

chickens that are specifically bred for large scale efficient meat production. They are known for

having very fast growth rates, reaching a slaughter weight of 2 kg in 6 to 7 weeks (32 days), a high

feed conversion ratio, low levels of activity and good meat yield (Aviagen, 2007; Anon., 2011).

These chickens are usually reared in total confinement, with environment and light conditions

controlled by the producer. If extreme variations occur in the climatic conditions, it may reduce the

growth performance of these chickens. The major market brand businesses in the South African

industry are Ross, Cobb, Hybro, Hubbard and Arbor Acres (DAFF, 2011b).

The Ovambo (Fig 3.5c) originated in the northern rural part of Namibia and Ovambo land

and the name refers to their geographical area. These chickens are predominantly dark coloured

and smaller in size. The Ovambo reaches sexual maturity in 143 days (Anon., 2010a; ARC, 2010).

Venda chickens (Fig 3.5d) were first described by Dr. Naas Coetzee in 1979 in the Venda

district in the Northern Cape Province of South Africa. These chickens are multi-coloured with

white, black and red as predominant colours and green on their feather tips. They reach sexual

maturity in 143 days (Anon., 2010a; ARC, 2010).

(a) (b) (c)

(d) (e)


34

The South African Naked neck (Fig 3.5e) is thought to have originated in Malaysia, and was

brought here by the European settlers. The naked neck is very colourful with red, white and black

coloured feathers; they reach sexual maturity in 155 days. These chickens have 30% fewer

feathers, and they can produce the same body weight with less feed (therefore a lower feed

conversion ratio) than other indigenous genotypes, they are also more heat tolerant (Anon., 2010a;

ARC, 2010).

Abdullah et al. (2010) investigated the carcass and meat quality characteristics of different

crosses of broiler strains and found that the different strain of bird had a significant effect on the

carcass weight, different portion weights, water holding capacity, tenderness, moisture content,

protein content and crude fat content. No significant differences were obtained for dressing

percentage and pH between the different broiler strains.

EFFECT OF GENOTYPE AND PRODUCTION SYSTEM

Morphology

Morphological properties refer to the carcass characteristics and the meat yield of a chicken

carcass.

Growth, slaughter weight and carcass yield

Growth is defined as the increase in size (weight or dimensions) of an animal (Jones, 2004; Warris,

2010). Animal growth resembles a growth curve called the sigmoid curve and consists of three

growth phases, slow, rapid and plateau (Jones, 2004; Lawrie & Ledward, 2006; Warris, 2010).

Animal tissue follows a precise order of maturation: firstly the nervous tissue followed by bone then

muscle and lastly fat (Warris, 2010). The growth rate of animals can be altered by various

environmental and nutritional circumstances (Aberle et al., 2001; Lawrie & Ledward, 2006).

Commercial or intensive production systems are associated with temperature, photoperiod

and light intensity controlled conditions, high energy diets, high plane of nutrition and high feed

efficiency rates which encourage rapid growth and the early onset of the fattening phase (Fanatico

et al., 2005b; Lawrie & Ledward, 2006). Extensive production systems, however, would be

exposed to fluctuating temperatures and increased exercise on the forage area (Fanatico et al.,

2005b). Therefore it would be expected that the animals from the intensive production system

would reach maturity at an earlier age and would produce heavier slaughter weight and carcasses

with more fat if slaughtered at the same age as the free range animals (Fanatico et al., 2005b).

This coincides with results found by Castellini et al. (2002a) where lower growth rates and carcass

weights of extensive birds compared to intensive birds were reported. However, Fanatico et al.

(2005b) and Bogosavljević-Bosković et al. (2009) reported that the production system had no

significant effect on the growth of the chickens and the carcass weight. On the other hand, Wang


35

et al. (2009) stated that the production system had an effect on the growth rate of the chickens, but

no effect on carcass yield.

Different genotypes of animals have different carcass conformation, growth rates and

curves (Warris, 2010). Therefore, slow growing chicken genotypes will take longer to attain the

same degree of maturity or body weight as a fast growing chicken genotype. Broilers (fast

growing) have been selected for rapid growth and reach market weight (2 kg) in 32 days, where

medium and slow growing chicken genotypes usually take 63 to 81 days, depending on the diet fed

(Gordon & Charles, 2002). Fanatico et al. (2005b) reported that the fast-, medium- and slow

growing genotypes reached a similar market weight in 53, 67 and 81 days respectively and

Bogosavljević-Bosković et al. (2009) found that the carcass yield of slower growing hybrids were

lower than fast growing birds.

Muscle weight

Muscle weight is a function of the fibre type, amount, length and relative size of the fibre and

increased muscle weight is mainly due to hypertrophy of fibres. The amount of muscle fibres are

determined by genetic and environmental factors and remain constant at birth (Lefaucheur &

Gerrard, 1998; Rehfeldt et al., 2000). Skeletal muscle hypertrophy, which occurs during the growth

phase of the animal, is affected by various factors such as hormones, nutrition, age and physical

activity (Jones, 2004; Warris, 2010). During exercise, the glycolytic IIb muscle fibres increase in

size (Taylor, 2004) and according to Lefaucheur and Gerrard (1998) glycolytic IIb muscle fibres

have a higher relative volume than the other fibre types. Therefore an increase in fibre IIb

proportion, during exercise, could lead to an increased muscle weight; typically found in

extensively reared animals. Consequently, the degree of increase in muscle weight will be

determined by the function of a specific muscle, period of exposure to exercise and the degree of

exercise.

Husak et al. (2008) reported that chicken wing and leg quarter yields increased when they

had access to an outdoor area, but the breast yield from intensive birds were higher than the

extensive birds. In contrast Castellini et al. (2002a; 2008) found yields of breast, thigh and

drumstick of outdoor birds to be higher than indoor birds. On the other hand, Fanatico et al.

(2005b), Bogosavljević-Bosković et al. (2009) and Wang et al. (2009) found no effect of the

production system on portion yield.

As mentioned, the amount of muscle fibres of an animal is genetically determined, therefore

different genotypes of chicken may have different amounts of fibres present which will

consequently affect the portion yield. According to Fanatico et al. (2005b), fast growing type birds

have the largest breast yield, the lowest wing yield (%) and the lowest leg quarter yield in the same

production system.


36

Physical

pH

At the time of slaughter, oxygen and nutrients that are supplied by the circulatory system are

stopped. Glycogen is metabolised in an anaerobic environment to lactic acid. The lactic acid

build-up causes a drop in pH and this helps in the conversion of muscle to meat. Normal post

mortem muscle pH (pHu) is approximately 5.5, but in chicken meat the pHu values are usually

higher, pHu ≥ 6.0 at 2 to 4 h post mortem (Honikel, 2004; Lawrie & Ledward, 2006; Nissen &

Young, 2006; Warriss, 2010). The rate of pH decline will have a large effect on meat quality

attributes such as colour, tenderness, water holding capacity (WHC), cooking loss, juiciness and

microbial stability or shelf-life (Fletcher, 1999; Honikel, 2004). Muscle pH affects the water binding

ability of proteins and therefore directly affects the physical structure of the meat and its light

reflecting properties (Briskey, 1964). A rapid decline in post mortem pH increases the risk of pale,

soft and exudative (PSE) meat and is associated with poor WHC and light meat (Fletcher, 1999;

Castellini et al., 2002a). A higher pHu increases the risk of dark firm and dry (DFD) meat and is

associated with darker colour meat and will be more susceptible to bacterial spoilage, thus poor

shelf life (Monin, 2004; Lawrie & Ledward, 2006; Husak et al., 2008). Generally speaking, a higher

pHu in meat is more effective for retaining desirable colour (more colour stable), moisture

absorption properties and better flavour (Warriss, 2010; Lawrie & Ledward, 2006; Husak et al.,

2008). On the other hand, a higher pHu value will also reduce the amount of post mortem

proteolysis and result in tougher meat products (Warriss, 2010 Fletcher, 2002; Lawrie & Ledward,

2006). Chickens in general, have a very fast pH decline and are more prone to PSE meat

(Fletcher, 2002; Lawrie & Ledward, 2006).

Studies on broilers showed that they are more likely to produce meat with a slower pH

decline, resulting in a higher pHu and better WHC, due to the selection for rapid growth and high

breast meat yield (Le Bihan-Duval et al., 1999; Berri et al., 2001, 2007). However, some studies

suggested that the selection for fast growth may have caused unfavourable effects on meat quality,

like PSE, especially when chicks are submitted to stressful conditions (Sandercock et al., 2001).

pH decline in slower growing chicken lines such as the Koekoek occur more rapidly than in faster

growing chicken lines such as the broiler resulting in a lower pHu, this is due to the fact that slow

growing chicken lines are frequently more susceptible to stress (Castellini et al., 2002a; Debut et

al., 2003; Berri et al., 2005; Debut et al. 2005).

Literature often notes that the meat of animals reared in extensive production systems,

which provide better welfare conditions and lower stress conditions, is characterized by lower pHu,

due to more glycogen being present at point of slaughter (Enfalt et al., 1997, Castellini et al.,

2002a; Fanatico et al., 2007a; Wang et al., 2009). However, recent studies by Ponte et al. (2008)

and Połtowicz and Doktor (2011) showed pH results of extensive meat to be typical of normal meat

and Husak et al. (2008) found no significant difference in pH between intensively produced and


37

free range broilers. The increased activity of animals during extensive rearing may result in more

type I and IIa (red) muscle fibres with a higher content of glycogen. Therefore, there would be a

higher anaerobic glycolytic potential in those muscles, especially in the thigh, during the anaerobic

post mortem glycolysis, resulting in a lower pHu post mortem (Lawrie & Ledward, 2006).

Colour

Colour is the main visual or appearance factor involved in the selection of a food when it comes to

consumers and consumers regularly select or reject a product based merely on its appearance

(Fletcher, 2002; Jahan et al., 2005). Fletcher et al. (2000) showed that consumers generally prefer

broiler meat colour ranging from pale tan to pink when raw and tan to grey when cooked. The

three major contributing factors to poultry meat colour are myoglobin content, pH of the meat, and

chemical state of the haem structure (Fletcher, 2002; Lawrie & Ledward, 2006). Muscle pH and

meat colour are highly correlated and this also affects the water binding nature of the proteins and

therefore directly affects the physical structure of the meat and its light reflecting properties as well

as the biochemical state and chemical reactions of the myoglobin (Fletcher, 1999, 2002; Lawrie &

Ledward, 2006). Lower muscle pH is associated with lighter meat, where the meat appears to be

less red and more yellow, and higher muscle pH is associated with darker meat (Castellini et al.,

2002a; Fletcher, 2002; Lawrie & Ledward, 2006). Myoglobin content has been shown to be related

to species, muscle, and age of the bird (Fletcher, 2002).

Meat colour is generally measured by a method recommended by the International

Commission of Illumination (CIE); the so called CIEL*a*b* measurement coordinates (Honikel,

1998). The L* coordinate of the CIEL*a*b* measurement signifies the lightness or reflection of the

sample (0 = black; 100 = white), the a* coordinate represents the red/green spectrum

(positive = red; negative = green) and the b* yellow/blue (positive = yellow; negative = blue). From

these values the hue-angle (°) and chroma value can be calculated.

It is evident from literature, that chickens from extensive production systems, produces

meat with a lower L* value (darker) and higher a* value (more red) when compared to intensively

raised chickens, which could be attributed to the higher myoglobin red type fibres content, due to

increased physical activity of these outdoor birds (Bogosavljević-Bosković et al., 2006; Husak et

al., 2008). The higher L* value of intensively reared chickens can also be ascribed to a higher lipid

content in the muscles, due to the high energy diet fed to these birds. Lipids have high light

reflection properties and the meat therefore appears lighter (Hedrick, 1983). However, when

broilers were given access to an outdoor area, there were no effect on their carcass colour

(Fanatico et al., 2007a; Połtowicz & Doktor, 2011), but when slow growing birds had access to an

outdoor area their meat became more yellow (higher b* value) (Fanatico et al., 2007a). However,

Husak et al. (2008) reported that breast and thigh meat of free range broiler chickens were less

yellow (lower b* value) than intensively reared broilers. With regard to genotype, slow growing


38

birds had a higher a* value (more red) than faster growing birds, due to a higher myoglobin

concentration in the muscles of the older birds (Miller, 1994; Husak et al., 2008).


Water holding capacity (WHC) is defined as the ability of the meat structure to hold water within its

fibres (Offer & Trinick, 1983). Meat consists of approximately 73-75% water (bound, free and

immobilized) (Lawrie & Ledward, 2006). The WHC of meat can be determined by calculating the

percentage drip- and cooking loss of meat (Honikel, 1998).

When muscle pH drops below the isoelectric point (< 5.2) of the muscle proteins (actin and

myosin myofibrillls), these proteins lose their net charge and therefore their ability to bind water

(Hamm, 1961 Warriss, 2010). When the muscle is then cut, excessive amounts of fluid oozes from

the cut surface over time, this undesirable occurrence is known as drip loss (Warriss, 2010). Meat

with a high drip loss, thus low WHC, have excessive amounts of moisture on the surface of the

meat, thus increasing the meat’s light scattering properties, causing it to appear lighter/pale

(Briskey, 1964; Warriss, 2010). Water contains valuable nutritional components (vitamins,

minerals, proteins and flavour components), and if water is lost during drip loss, the nutritional

quality of the meat decreases (Hamm, 1961).

Cooking loss is the amount of moisture released by the meat during cooking when the

muscle proteins denature, causing structural changes in the tissue of the meat (Honikel, 2004).

Denaturation causes the sarcoplasmic and myofibrillar proteins to coagulate, thus shrinkage of the

protein myofilaments occur and the water between these fibres are expelled (Honikel, 1998;

Warriss, 2010). The amount of moisture lost during cooking is determined by the pHu of the meat.

Meat with a high pHu will have a lower cooking loss compared to meat with a low pHu (Honikel,

2004; Lawrie & Ledward, 2006) and the resulting meat products will be perceived as being dry

(Warriss, 2010). The muscles of chickens exposed to extreme pre-slaughter stress have a low

pHu, consequently increasing the cooking loss of the meat (Castellini et al., 2002a; Debut et al.,

2005; Lawrie & Ledward, 2006). Chatrin et al. (2006) found that breast muscles with higher lipid

content will have an increased cooking loss. Drip loss is inversely correlated with the cooking loss

of meat, therefore if the drip loss of a sample increases the cooking loss decreases (Thomas et al.,

2004).

Castellini et al. (2002a, b) found a higher cooking loss in extensively reared birds than in

intensively reared, due to a lower muscle pH. A higher WHC and lower cooking loss was recorded

in free range reared chicken breast meat by Fanatico et al. (2007b) and Husak et al. (2008) than in

intensively reared chicken breast. These results are contradictory to the theory and to Castellini et

al.’s (2002b) studies where lower muscle pH is most likely to result in reduced WHC. However,

Husak et al. (2008) and Qiao et al. (2001) found that lower pH, nearer to the isoelectric point of

protein from free range meat had a better WHC capacity; these results suggested that other factors

such as protein and moisture content may have an external effect on the WHC of the meat. When


39

considering genotype, Lonergan et al. (2003) and Fanatico et al. (2005a) reported a higher cooking

loss in slow growing birds than in fast growing birds, this was due to a higher lipid content in the

muscle. If total moisture loss (drip- and cooking loss) is measured, then slow growing chicken

genotypes have better WHC than fast growing chicken genotypes (Fanatico et al., 2007a).

Instrumental tenderness

Tenderness is considered the most important palatability characteristic of meat and a primary

factor of quality by consumers (Boleman et al., 1997; Fletcher, 1999; Jahan et al., 2005; Lawrie &

Ledward, 2006; Destefanis, 2007). Tenderness can be evaluated by objective methods,

instrumental or sensorial with trained panels, or by subjective methods, with a consumer panel

(AMSA, 1995). Objective methods allow the comparison of different treatments as well as

determining their effect on a specific characteristic, but do not provide information about product

acceptability or preference of a specific sample (Destefanis, 2007). The most widely

acknowledged method used for objectively evaluating the toughness of raw and cooked meat is

the Warner Bratzler shear force test (Miller et al., 1995; Boleman et al., 1997). Meat is sheared

vertical to the muscle fibre direction and a tougher meat sample will have a higher resistance to

shearing. Destefanis (2007) noted that instrumental tenderness measurements are positively

correlated with sensory tenderness. Toughness or tenderness of meat is affected by various

factors of which marbling, connective tissue type and content, enzymatic ageing and muscle

shortening are only a few (Miller et al., 1995). Marbling or intramuscular fat (IMF) content of meat

is associated with intensive production systems, and is positively correlated with meat tenderness

(Castellini et al., 2002a, 2002b, 2007; Zhao et al., 2007; Chartrin et al., 2006). Therefore muscles

containing more type I and IIa red fibres with higher fat content will be more tender than muscles

containing type IIb white fibres with less fat content (Lawrie & Ledward, 2006). The size and

diameter of a fibre also affects the tenderness of meat. Type I red fibres have the smallest fibre

size and type IIb white fibres the biggest, while Type IIa red fibres have an intermediate size

(Maltin et al., 1997; Mckee, 2003; Taylor, 2004). Maltin et al. (1997) stated that, prior to the onset

of post mortem proteolysis; meat with larger muscle fibres tends to be less tender than meat with

smaller fibre diameter. The tenderisation or ageing of meat is also endorsed by post mortem

proteolysis, which is activated by proteolytic enzymes (calpains) and inhibited by the presences of

proteolysis inhibitors (calpastatins) (Lawrie & Ledward, 2006). When adenosine triphosphate

(APT) is depleted ante mortem, there is no post mortem pH drop and the sarcomeres in the muscle

do not shorten, therefore resulting in tender meat (Warriss et al., 1999). According to Warriss et al.

(1999) poultry meat is considered to be tender.

Husak et al. (2008) reported that the breast meat of intensive chickens were more tender

than those of free range chickens, but Castellini et al. (2002b) found extensive reared meat to be

more tender and Fanatico et al. (2005a) found no difference in production system regarding

tenderness. According to Smith and Carpender (1970) and Lewis et al. (2005), muscles with a


40

high level of physical activity will result in tougher meat due to increased intramuscular collagen

content. Farmer et al. (1997) found, when comparing two different genotypes of chickens, that

genotype and diet contributed the most to textural attributes.

Chemistry/Nutritional value

Chicken meat, also called white meat, is well known for its superiority in health features compared

to red meat, mainly because of its low fat and cholesterol contents (Charlton et al., 2008). Meat

primarily consists of five chemical constitutes: moisture (water), proteins, lipids (fats),

carbohydrates and inorganic matter (ash or minerals) (Keeton & Eddy, 2004).

Moisture

Lean meat comprises approximately 72-75% water (Kauffman, 2001; Keeton & Eddy, 2004). The

moisture content of meat contributes to numerous meat palatability traits such as juiciness,

tenderness and flavour (Lawrie & Ledward, 2006). These three effects are considered to be the

main factors that influence overall consumer acceptability and palatability of meat (Beilken et al.,

1990; Warriss, 2010). There is a contradiction in literature about the moisture content of animals

reared in different production systems. Bogosavljević-Bosković et al. (2009) reported no significant

difference in the moisture content of breast muscle for intensively and free range reared birds

whilst Husak et al. (2008) and Fanatico et al. (2005a) found that the moisture content of free range

reared birds was lower than the intensively reared birds. However according to literature, the

moisture content of meat is inversely correlated with the fat content of the muscle (Pearson &

Young, 1989), therefore in theory if a meat sample has a low fat content, it will have high moisture

content. As previously mentioned, free range reared chickens generally have a lower fat content,

and will consequently have higher moisture content than intensive birds.

With regards to genotype, Fanatico et al. (2005a) established that slow growing birds had a

higher percentage moisture than fast growing birds. Fanatico et al. (2005a) also reported that the

interaction between genotype and production system had no significant effect on the moisture

content of the meat.

Crude protein

Lean chicken meat is a valuable source of protein (16-20%) which is rich in essential amino acids

(lysine, leucine, isoleucine, sulphur containing amino acids) (Kauffman, 2001; Keeton & Eddy,

2004). It is known that the protein of meat decreases with an increased fat content (Keeton &

Eddy, 2004). Therefore it would be expected that free range reared birds contain a higher

percentage protein, due to their lower fat content, than intensively reared birds. This theory

corresponds with the findings of Husak et al. (2008) and Bogosavljević-Bosković et al. (2009)

where higher protein contents were reported in extensively reared birds’ meat.


41

It would also be expected that the slow growing birds would contain a higher percentage

protein in their meat than the fast growing birds, since they are late maturing and will contain less

fat. Studies by Fanatico et al. (2007a) and Husak et al. (2008) confirm this where they reported

higher protein contents in the slower growing birds.

Total lipid content and fatty acids

Animal muscle tissue is comprised of approximately 2.5 – 5% fat, containing phospholipids, neutral

lipids (triglycerides) and cholesterol (Kauffman, 2001; Keeton & Eddy, 2004). Poultry meat is

known for being low in fat (lean), with white meat (breast) having as low as 3% and red meat (thigh

and drum) 7.3% fat (Parkhurst & Mountney, 1988; Mckee, 2003; Fanatico et al., 2007a). Red

muscles store intramuscular fat (IMF) within the muscle fibres, in the form of fat droplets and they

normally have higher IMF contents compared to white muscles (Lawrie & Ledward, 2006).

However the fat of poultry, unlike other meat animals, is mainly deposited in the abdomen or

subcutaneously (under the skin) or between muscles rather than in the meat itself (IMF) and will

therefore have corresponding lower lipid and higher moisture, protein and ash contents than other

meat animals (Parkhurst & Mountney, 1988; Fanatico et al., 2007a)

The composition of lipids in poultry is affected by several factors such as genotype, gender,

age, weight, location of fat deposition in the carcass, environmental temperature and nutrition.

Differences in the fat content between species and muscles are often a result of the differences in

the muscle fibre types (Lawrie & Ledward, 2006). It is generally known that the red fibre muscles,

like those in the thigh and drum stick, have a higher amount of triglycerides and phospholipids than

white muscles and therefore contain a higher percentage of PUFA (Wood et al., 2004).

The presence or absence of lipids plays a key role in the final meat quality, positively and/or

negatively (Enser, 1999; Wood et al., 2003). The IMF of meat is a good source of essential omega

3 (n-3) and omega 6 (n-6) fatty acids as well as fat-soluble vitamins (A, D, E and K) which are

important for human nutrition and health (Keeton & Eddy, 2004; Charlton et al., 2008). During

mastication, the IMF of the meat stimulates the secretion of saliva, increasing the sustained

juiciness of the meat as perceived by consumers (Lawrie & Ledward, 2006). The type of fatty

acids present, together with the cooking process and Maillard reactions, produce volatile

components and oxidation products that contribute to meat flavour and odour (Mottram, 1998;

Wood et al., 2003). Fatty acids also have different melting points and therefore the variation in

fatty acid composition affects the firmness and elasticity of the fat present in the meat, whether it is

intermuscular or intramuscular fat (Wood, et al., 2003). The IMF content, fatty acid composition

and unsaturated phospholipid fatty acids present in meat, therefore, directly affect the appearance,

sensory properties, flavour and juiciness, and indirectly the tenderness of meat (Enser, 1999;

Wood et al., 2003). Consequently, meat with low IMF levels will be less flavoursome and dry. The

health conscious consumers demand lean meat, but still want the same taste experience which

high in fat products have to offer. This task makes it extremely difficult for the meat industry to


42

produce low fat meat products with good palatability traits. With regard to taste, fat in meat may be

favourable in a gourmet market, but lean meat is advantageous in a health/diet driven market,

therefore fat content in poultry need to be thoroughly analysed and marketed as a speciality

product (Fanatico et al., 2005a).

Extensively produced chicken meat has a lower percentage IMF than intensively produced

chicken meat, this is due to increased physical activity and myogenesis being favoured over

lipogenesis in the former (Castellini et al., 2002a, 2002b, 2007, Fanatico et al., 2007a; Husak el al.,

2008). However, Fanatico et al. (2005a) reported no significant difference in IMF for production

system. With regard to genotype, some studies showed that slower growing birds contained less

fat than fast growing birds (Fanatico et al. 2005a, 2007b). In general the meat from older birds will

contain more fat with a higher SFA and lower PUFA than younger birds (Lawrie & Ledward, 2006;

Fanatico et al., 2005a) reported that the effect of production system and genotype had no

significant effect on the meat quality in their studies.

As previously mentioned, lipids consist of storage triacylglycerols and phospholipids

(structural lipids) (Enser, 1999). The latter tend to contain high concentrations of stearic (C18:0)

and lower concentrations of oleic (C18:1) and palmitic (C16:0) acid than triacylglycerols, but is

characterised by containing significant amounts of PUFA. Chicken meat has a very high

percentage of phospholipids, due to its low IMF and therefore is very rich in PUFA (Lawrie &

Ledward, 2006). Triacylglycerols contain one glycerol molecule and three long chain fatty acids

(Keeton & Eddy, 2004) and are variable due to the manipulation of dietary fatty acids and are

mainly made up of oleic (C18:1), palmitic (C16:0), linoleic (C18:2), stearic (C18:0) and palmitoleic

(C16:1) acids and very few PUFA (Enser, 1999). The latter can be classified as saturated (no

double bonds), monounsaturated (one double bond in the carbon chain) and polyunsaturated (two

or more double bonds in the chain) (Keeton & Eddy, 2004). The IMF content and the main fatty

acids present in bird fat are palmitic acid, palmitoleic acid, oleic acid, stearic acid and linoleic acid

with oleic acid being the highest (Gunstone & Russell, 1954; Enser, 1999; Lawrie & Ledward,

2006).

The total fat content, PUFA:SFA and the n-6:n-3 ratios are the three main factors when

considering the nutritional value and health consumption of meat (Enser et al., 1998). Raes et al.

(2004) suggest that a PUFA:SFA of > 0.7 and a n-6:n-3 ratio of < 0.5 contributes to the healthiness

of meat products. As previously mentioned, various studies have been conducted to increase the

PUFA concentration and lower the n-6:n-3 ratio in chicken meat by manipulating the fatty acid

content of feeds using feedstuffs such as fish oils, fish meal, soybean, linseed and rapeseed.

However, this operation must be thoroughly examined and controlled, since too high PUFA could

have a negative effect on the meat quality and human health (Enser, 1999; Wood & Enser, 1997;

Wood et al., 2003).

Unsaturated fatty acids are more susceptible to oxidation, causing off-flavours in meat and

shortening their shelf life, this phenomenon thus limits the production of meat with a much higher


43

PUFA:SFA ratio (Enser, 1999; Warriss, 2010; Wood et al., 2003). However this tendency of

PUFAs to oxidise is essential for flavour development during cooking (Wood et al., 2003). Overall

the PUFA:SFA ratio from the meat of monogastric animals is higher than in ruminants (Wood &

Enser, 1997; Enser et al., 1998). It is generally accepted that most of the SFAs increase low

density lipoprotein (LDL) cholesterol and PUFAs somewhat lower LDL cholesterol levels (Raes et

al., 2004; Ruxton et al., 2005). Chicken meat has a favourable fatty acid ratio, i.e. a high content of

PUFA and a low content of SFA (Charlton et al., 2008). This favourable ratio (< 0.7) lowers human

blood cholesterol levels making chicken meat a very healthy product for consumption (Raes et al.,

2004).

It is general knowledge that chicken meat has a favourable fatty acid ratio and low

cholesterol content and therefore is considered as a healthy product (Charlton et al., 2008).

However a few studies have shown that free range chicken meat have higher PUFA:SFA and

lower n-6:n-3 ratios, making it an even more favourable product than intensively produced chicken

meat (Castellini et al., 2002a; Jahan & Paterson, 2007; Husak et al., 2008). It is expected that free

range chicken meat products would contain more n-3 PUFA, since the diet should include pasture,

which is a good source of α-linolenic acid (18:3n3) (Ponte et al., 2008; Jahan & Paterson, 2007).

Ash

Meat contains approximately 1-2% ash, which is the mineral constituent (iron, potassium,

phosphorus, oxides, sulphates, silicates and chlorides) of meat; these are all essential for human

nutrition (Keeton & Eddy, 2004; Lawrie & Ledward, 2006). Many authors have established that

production systems have no significant effect on the ash content of meat (Castellini et al., 2002a;

Hoffman et al., 2004 Fanatico et al., 2005b, 2006; Kishowar et al., 2005; Bogosavljević-Bosković et

al., 2006) whilst Fanatico et al. (2005a) found that the effect of production system and genotype

had limited influence on the ash content. If a higher ash content in extensive production systems

were detected, it could be ascribed to a higher meat binding capacity, improved capillarisation of

muscles due to aerobic exercise and a higher heam pigment concentration (reviewed by Olsson &

Pickova, 2005). This phenomenon can also be ascribed to higher IMF content of meat in intensive

production systems as it is known that an increase in IMF content decreases the ash content of

meat (Keeton & Eddy, 2004). From van Marle-Köster and Webb’s (2000) results it can be seen

that there was a significant difference between the ash content of the Koekoek and the Cobb

broiler (Table 3.5), thus it can be argued that chicken genotypes do have an effect on the ash

content.


44

Table 3.5 Proximate analysis of different South African indigenous chicken genotypes (Modified

from Van Marle-Köster & Webb, 2000)

Genotype Moisture (%) Ash (%) Crude Protein (%) Crude Fat (%)

Koekoek 64.6ab 3.9ab 46.1a 28.5a

Naked-Neck 64.1ab 3.9ab 45.2ab 34.9b

Lebowa-Venda 68.6a 4.7b 49.6d 28.8a

Ovambo 61.5b 2.7c 44.8ab 36.0bc

Cobb 65.6ab 2.4c 39.9c 40.6c

abMeans in columns with different superscripts are significantly different at P ≤ 0.05

Sensory attributes

Sensory flavour and aroma

The eating quality of meat involves three main attributes, namely tenderness (texture), juiciness

and flavour which are the major contributors to the consumers’ acceptability of meat (Warris, 2010,

Jahan et al., 2005). The flavour of meat is a combination of the sensations perceived by the

senses; taste and smell. Taste is perceived by the taste buds on the tongue and other parts of the

mouth, and mainly includes the four taste sensations: sweet, sour, salt and bitter. The sense of

smell or aroma is detected by the olfactory system when certain chemicals stimulate the receptors

(Farmer, 1999; Lawrie & Ledward, 2006). Flavour and aroma are greatly affected by the fatty acid

profile of the meat, as the thermal degradation of the lipids is one of the fundamental processes in

producing the aroma volatiles (Mottram, 1998). Unsaturated fatty acids can sometimes cause off-

flavours and -odours, because oxidation may occur and cause rancidity (Wood et al., 2003).

Extrinsic factors that affect meat flavour are feed, genotype, age and production system (Lawrie &

Ledward, 2006)

Chickens are monogastric birds and the dietary lipids from the feed are directly

incorporated into the tissue lipids without any modification (Wood & Enser, 1997). Accordingly the

type of feed is a major determinant factor in flavour development in chickens.

According to Lawrie and Ledward (2006) and Elmore et al. (2006), extensive animals have

more intense flavour, since they are usually older in age and more fat can be deposited for more

flavour development. Animals reared in an extensive production system have higher n-3

polyunsaturated fatty acids (PUFA) in their meat, in particular log-chain EPA and DHA (Castellini et

al., 2002a; Jahan & Paterson, 2005). When n-3 lipids are heated, they will break down to give

compounds that are more unsaturated and reactive than those of the n-6 fatty acids when broken

down. These compounds then react with Maillard precursors and appear to catalyse the

breakdown of more saturated fatty acids to affect, as well as contribute to, the meat flavour

(Elmore et al., 1999).


45

There is contradiction in the literature about the effect of production system and flavour

development in chicken meat. Farmer (1999), Kishowar et al. (2005) and Husak et al. (2008)

found that there was no significant difference in flavour between free range and intensively reared

chicken meat when slaughtered at the same age. However, significant differences were found in

flavour between free range and intensively reared chickens when they were not slaughtered at the

same age (Fanatico et al., 2006, 2007a).

Rural or indigenous chicken meat is firmer and more strongly flavoured than broiler meat

and consumers sometimes find this flavour development more palatable than the bland taste of

broiler meat (Jahan et al., 2005; Grashorn & Serini, 2006). This phenomenon is due to the fact

that rural or indigenous chickens are slow growing birds, thus being older in age than broilers,

which are fast-growing birds, at slaughter (Fanatico et al., 2005a, 2006, 2007a). Older animals

have increased concentrations of nucleotides in muscle, which degrade to inosinic acid and

hypoxanthine after death possibly contributing to the more developed flavour of older animals

(Aberle et al., 2001)

Sensory juiciness

Juiciness has two organoleptic components, initial and sustained juiciness. These two words are

also used by sensory panels as descriptors in cooked meat (Lawrie & Ledward, 2006). Initial

juiciness is defined as the amount of fluid released by the cut surface of meat during compression

between the forefinger and thumb (AMSA, 1995). Initial juiciness of meat is positively correlated

with the WHC of meat, which is influenced by the muscle’s pHu post mortem (Offer & Trinick,

1983). Chickens reared in an extensive production system are more prone to ante mortem stress

than chickens reared intensively (Debut et al., 2003; Berri et al., 2005; Debut et al. 2005). This is

due to the fact that extensive chickens are frequently not used to human handling during rearing

and when being caught before slaughter experience higher levels of stress (Mulder, 1999). Pre-

slaughter stress activates ante mortem muscle glycogen depletion and results in a high ultimate pH

post mortem (Fletcher, 1999; Warriss, 2010; Lawrie & Ledward, 2006). Therefore, chickens reared

extensively could have a higher pHu with a higher WHC, resulting in a higher initial juiciness score

compared to intensively reared chickens.

Sustained juiciness is defined as the perceived juiciness after a few seconds of chewing.

Sustained juiciness is affected by the presence of fat as fat stimulates the secretion of saliva and

thus improves juiciness (Lawrie & Ledward, 2006). An animal in an intensive production system

has a higher average daily weight gain compared to an animal in an extensive production system

and extensive production animals use energy to exercise (Castellini et al., 2002a). Therefore,

chickens in an intensive production system will have a higher carcass weight with more fat causing

it to be juicier, than extensively reared chickens. However, no significant difference in juiciness

was found by Kishowar et al. (2005) and Husak et al. (2008) between free range and intensively

reared chickens. This could be because the chickens were slaughtered at the same age and not


46

the same level of physiological maturity. Sonayia et al. (1990) found that slow growing chicken

lines were juicier compared to fast-growing chicken lines.

Sensory tenderness

As mentioned, tenderness is considered the most important palatability characteristic of meat and

a primary factor of quality by consumers (Boleman et al., 1997; Fletcher, 1999, 2002; Jahan et al.,

2005; Lawrie & Ledward, 2006; Destefanis, 2007). Tenderness refers to the force needed to

shear, squeeze, cut and ground meat during chewing and consumption (Pearson, 1963). Miller et

al. (1995) reported that consumers can easily distinguish between different meat tenderness levels

and that they are willing to pay more for a certified tender meat cut.

Castellini et al. (2002b), Wattanachant et al. (2004) and Fanatico et al. (2005a) reported

that faster growing chicken genotypes have more tender meat than slow growing chicken

genotypes. This phenomenon can be ascribed to the formation of more stable collagen cross-

linkages between muscle fibres from slow growing chickens; collagen cross linkages also increase

with age (Fletcher, 1999; Castellini et al., 2008). On the other hand, Farmer et al. (1997) obtained

significantly higher scores for meat tenderness from slower growing birds. Then again, in a later

study, Fanatico et al. (2006) found that that breast meat of medium growing birds were more

tender than fast and slow growing genotypes, however all treatments were scored as “slightly to

moderately tender”. Dransfield and Sosnicki (1999) suggested that reduced protein catabolism

could be the main reason for abridged tenderization of meat in modern fast growing chicken lines.

Calpains and cathepsins (proteins situated in the muscle fibres) are involved in the post mortem

proteolysis process and weakening of the muscle fibres producing tender meat (Dransfield &

Sosnicki 1999; Lawrie & Ledward, 2006). The higher degree of maturity of fast-growing birds at

the same age and increased growth and muscle mass, leads to reduced protein catabolism

(Dransfield & Sosnicki, 1999). This reduced protein catabolism leads to less activity of post

mortem proteolysis and, therefore less tenderization of meat (Dransfield & Sosnicki, 1999).

CONCLUSIONS

The modern consumer wants quality meat, as associated with the intensive meat broiler, but also

demands products that are healthy, environmentally friendly, promote sustainability and comply

with animal welfare guidelines. Only medium and slow growing chicken genotypes can completely

benefit from an extensive production system, since fast growing genotypes have the habit of being

inactive, staying indoors and do not participate in any activity involving flying, foraging and running.

To understand the full impact of rearing system and genotype on chicken meat quality under South

African conditions, a complete study needs to be done on the meat characteristics of broiler (fast

growing), a South African indigenous chicken (slow growing) and a hybrid (medium growing)

genotype, to ensure consumer expectations are met and the quality is maintained.


47

Therefore the overall objective of this study is to investigate the impact of production

system (free range and intensive) and chicken genotype (Broiler, Potchefstroom Koekoek, Ross X

Koekoek hybrid) on the meat quality characteristics by using various physical, chemical, sensory

and consumer analyses.

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CHAPTER 4

EFFECT OF REARING SYSTEM ON GENOTYPE ON THE GROWTH, CARCASS AND INDIVIDUAL PORTION YIELD OF CHICKEN

ABSTRACT

Consumer interest in free range poultry production as well as free range products is growing. In

South Africa, little information is available on the effect of this system on the production indicators

of chicken. This experiment was conducted to evaluate the effect of production system and

genotype on the growth and production efficiency as well as carcass and individual portion yield of

chicken. Fast growing (broiler), slow growing (Potchefstroom Koekoek) and Hybrid chickens were

reared for 42, 56 and 91 days, respectively in either a commercial production system or under free

range conditions. For each genotype the free range chickens produced heavier (P ≤ 0.05) live

weights than intensive reared chickens. The broilers had the best (P ≤ 0.05) feed conversion ratio

(FCR), highest average daily gain (ADG) and European production efficiency factor (EPEF),

followed by the Hybrid and then the Potchefstroom Koekoek. The broilers had the highest

(P ≤ 0.05) breast yield (%) and the lowest (P ≤ 0.05) thigh, drumstick and wing yield (%), whereas

the Hybrid and Koekoek produced higher (P ≤ 0.05) thigh, drumstick and wing yields. Production

system also had an effect (P ≤ 0.05) on the portions and free range rearing produced higher

breast, thigh, drumstick and wing yields. Overall the growth and morphological attributes of the

chickens were more strongly influenced by genotype than production system; therefore the latter

should have no direct impact on the consumer acceptability of the meat. It would seem that the

Hybrid could be a possible alternative for free range rearing.

Keywords: Broiler, Potchefstroom Koekoek, Ross x Koekoek hybrid, Morphological composition

Portion yield, Meat quality, Production system, Genotype


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INTRODUCTION

The modern consumer is changing from products produced in intensive production systems to,

what they perceive as, more sustainable and environmentally friendly produced products. The

major reason for this shift is that consumers believe that the latter provide better, healthier and

more nutritious products that taste better (Sundrum, 2001; Fanatico et al., 2007; Branciari et al.,

2009). In meat, the interest of the consumer has also grown towards quality aspects, rather than

quantity; this mind shift has provided opportunities for market segmentation of more speciality

products, such as free range and organic branded products.

Commercial poultry production, especially intensive broiler production, has shown a rapid

increase and has dominated the South African agricultural sector over the past decade (Anon.,

2012a; FAO, 2012). However, a new segment that is growing locally is the production and sale of

free range chickens. In South Africa, the normal fast growing commercial broiler is currently used

for both free range and intensive production systems. These chickens reach market weight as

early as 32 days. However, this rapid growth has led to concerns about animal welfare, since

more leg disorders and higher mortality rates occur. Castellini et al. (2002a) reported that only

slow-growing chicken stains can completely benefit from an extensive rearing system. There is

also the question on what the effect of a free range production system would be on the

organoleptic quality of chickens? Dransfield and Sosnicki (1999) and Le Bihan-Duval et al. (1999)

previously reported that selection for fast growth and high yield are likely to affect the sensory and

functional qualities of the meat, therefore it is possible that differences in meat quality may exist

between fast and slow growing broiler strains (Fanatico et al., 2005). Lonergan et al. (2003)

compared meat quality of chickens with different growth rates i.e. broilers, Leghorns and their

crosses and reported high variation in composition and quality characteristics of breast meat.

Factors that determine the value of a chicken carcass include the carcass weight, the yield

of meat and the quality of lean meat. Chickens are usually sold as portions, making it very

versatile and convenient for the modern consumer (Kennedy et al., 2004). Deboned portions and

skinless chicken portions are also sold, making it even more convenient albeit more expensive.

The importance of the carcass and muscle yield of the bird is therefore emphasized. A few studies

have already evaluated the growth, carcass and portion yields from fast-, medium- and slow-

growing birds, but there is large variation in the production systems and type of birds (genotype,

strain and age) used (Castellini et al., 2002a; Lonergan et al., 2003; Quentin et al., 2003; Fanatico

et al., 2005; Husak et al., 2008). Such studies have never been done in a South African

environment or on indigenous chickens cross bred with commercial broilers.

This study was undertaken to gain information on the production and morphological

properties of three different chicken genotypes found in South Africa: Broiler (B) (Cobb 500), Ross

308 X Potchefstroom Koekoek hybrid and Potchefstroom Koekoek (K) reared in intensive and free

range environments. The aim of this study was to investigate the effect of chicken genotype and

production system (intensive (I) or free range (FR)) on the growth, production efficiency, carcass


60

and individual portion yield of chickens. This study did not include the quantification of the effect of

gender (male or female) on the growth, production and carcass yield.


Experimental birds, location, handling and slaughter procedure

Two hundred crossbred (Ross 308 roosters X Potchefstroom Koekoek hens) chicks were hatched

at Mariendahl, (33° 51’ 0 S; 18° 49’ 60 E) Experimental Farm, Stellenbosch University, situated in

the Western Cape, South Africa. Purebred one day old Potchefstroom Koekoek chicks (n = 200)

were flown from the Agricultural Research Council – Animal Production Institute (ARC-API)

(Pretoria, Gauteng, South Africa) and 200 one day old Cobb 500 (Broiler) chicks were purchased

from Tydstroom hatchery near Hermon (Western Cape, South Africa) and brought to Mariendahl.

Each chick was vaccinated against infectious bursal disease (IBD) at one day of age and

Newcastle disease at one and 18 days of age. After individual weighing and tagging the one day

old chicks were randomly assigned to two rearing systems; intensive (n = 100 per genotype) and

extensive/free range (n = 100). Genotypes were maintained separately. All chickens were fed ad

libitum the same complete commercial type diet consisting of a starter, grower and finisher feed

(Table 4.1). Feed was allocated at the chicks at a volume of 900g starter, 1200g grower and

finisher until slaughter.

Intensive production system

At day one of age, the BI, HI and KI chicks were placed into a bioassay unit (intensive system).

The chicks were grouped according to genotype for each treatment. This unit comprises of a

temperature controlled room equipped with wire cages (0.3 x 0.25 m; 53 birds/m2). Management

practices described by ROSS International were followed (Aviagen, 2009). Artificial lighting was

provided at a pattern of 16 h of light altering with 8 h of darkness. Ventilation in the house was set

to provide a minimum of six air changes per hour. At the age of 14 days, the chicks were moved to

a chicken house equipped with wire cages (0.9 x 0.6 m; 14 birds/m2) (Fig. 4.1a), each containing a

tube feeder and two nipple drinkers. Again the chicks were grouped according to genotype. The

temperature in the room was controlled and decreased as they grew from 33°C to 15°C and

ventilation in the house was set to provide a minimum of six air changes per hour. Artificial lighting

was provided at a pattern of 16 h of light alternating with 8 h of darkness.


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Table 4.1 Ingredient (%) and calculated nutrient composition of commercial diets fed to intensively

and extensively reared chickens

Ingredients (%) Starter Grower Finisher

Maize 61.59 65.76 59.66

Fish meal 65 9.79 10.00 -

Soybean full fat 16.85 18.84 36.13

Soybean 46 8.87 3.00 -

L-lysine HCL 0.27 - 0.20

DL methionine 0.27 0.21 0.31

L-Threonine 0.14 0.05 0.11

Vitamin + mineral premix 0.15 0.15 0.15

Limestone 0.80 1.01 1.58

Salt - 0.05 0.25

Monocalcium phosphate 0.84 0.75 1.45

Sodium bicarbonate 0.43 0.17 0.17

Total 100.00 100.00 100.00

Calculated nutrient composition

AMEn* chick 12.50 12.90 13.00

Crude protein % 22.54 20.73 18.97

Dry matter % 88.22 88.03 88.20

Lysine % 1.52 1.21 1.17

Methionine% 0.69 0.62 0.59

Crude fat % 6.57 7.03 8.95

Calcium % 0.90 0.96 0.92

Avail. Phosphorus % 0.50 0.48 0.45

*Nitrogen-corrected apparent metabolizable energy value (AMEn)

Extensive production system

The day old BFR, HFR and KFR chicks were placed in small pens (2.7 x 3.5 m) with deep wood

shavings in an indoor chicken house facility. The chicks were grouped according to genotype for

each treatment in the pens. The initial density of each pen was 10.5 birds/m2. Artificial lighting

was provided at a pattern of 16 h of light altering with 8 h of darkness and ventilation in the house

was set to provide a minimum of six air changes per hour. At 21 days of age, the chicks were

moved outside to a larger facility (Fig. 4.1b). This facility was naturally ventilated. The house was

subdivided into three “indoor” pens that opened into three separate yards, which were surrounded

by chicken wire. The “indoor” areas of each pen measured 1.5 x 3.0 m and contained fresh wood

shavings and infrared light heaters that were used to maintain night temperatures above 15°C.

Birds were allowed unlimited access to the “outdoor” area. The “outdoor” area consisted of a

concrete floor area covered with shading (3.0 x 4.5 m) and an open air grassy area (3.0 m x 6.0

m). Each pen measured 3.0 x 12.0 m (2.8 birds/m2). The grassy area was completely covered


62

with natural growing vegetation (mainly kikuyu grass). The outdoor and indoor areas were

provided with automatic drinkers as well as chicken feeders allowing for ad libitum access.

Photoperiod was limited natural daylight (~15 h of daylight and 9 h of darkness). Management

practices described by the SAPA code of practice 2012 under the section free range Broiler

production were followed (Anon., 2012b).

Figure 4.1 (a) Intensive production wire cages; (b) Extensive production housing pens.

Data collection

Body weights of all the chickens were determined at day old and weekly thereafter (intensive n = 8

groups; free range n = 1 group). Feed was supplied ad libitum and weekly intake was determined.

Daily mortalities were recorded. Data were used for the calculation of feed conversion ratio (FCR),

average daily gain (ADG), and the European production efficiency factor (EPEF) (Awad et al.,

2009). The FCR, ADG and EPEF were calculated as follows:

Feed conversion ratio = (Cumulative feed intake per chick / Average live weight per chick)

Average daily gain = (Average live weight per chick at slaughter day - Average live weight per

chick at day 0) / Age (days)

European production efficiency factor = ((*Liveability % x Live weight) / (Age (days) x FCR)) x 100

Slaughtering

At the age of 42, 56 and 91 days respectively, 100 broiler, 100 Ross X Koekoek hybrid chickens

(n = 50 per genotype per production system) were selected within a target weight range of 2.0 to

* Liveability % (Percentage of birds alive at that given time/age).

(a) (b)


63

2.3 kg, weighed and slaughtered, according to acceptable commercial standards through

immobilization by electrical stunning (50-70 volts; 3-5 s), followed by exsanguination, defeathering

and evisceration. The Potchefstroom Koekoek (n = 50 per genotype per production system) were

slaughtered at 91 days of age with an average weight of 1.6 kg, as it would have taken them too

long to reach an average weight of 2.0 kg. After evisceration the carcasses were chilled at 4°C for

approximately 12 hr. After chilling the carcasses were transported to the meat science laboratory

at Stellenbosch University. It should be noted that due to the sampling procedure, the live weights

and therefore carcass weights of the birds slaughtered may differ from the mean live weights of the

whole group.

Experimental units

At the meat science laboratory each carcass was weighed and the cold carcass weight recorded.

Thereafter the carcass was divided into commercial cuts (breast, drumstick, thigh and wing) using

a portioner. First the carcass was cut into half. Then the thighs and drumsticks were removed

from the half carcasses by cutting above the thigh towards the acetabulum and behind the pubic

bone. The thighs and drumsticks were then separated from each other by cutting perpendicular to

the joint between the drumstick and thigh bones. The wings were removed by cutting the joint

between the scapula and the coracoid. The separate portions were then weighed and the portion

weights recorded. Thereafter all the portions, except for the wing was dissected into lean, skin

and bone and weighed. The portions were then vacuum-packed and frozen at -18°C until further

analysis. The experimental treatments included six meat units which consisted of either a broiler, a

Hybrid or a Koekoek sample each reared intensively or free range. The following acronyms are

used to describe the six different treatments:

BI – Broiler intensive; BFR – Broiler free range; HI – Ross X Potchefstroom Koekoek hybrid

intensive; HFR – Ross X Potchefstroom Koekoek hybrid free range; KI – Potchefstroom Koekoek

intensive; KFR – Potchefstroom Koekoek free range.

An experimental unit consisted of n = 50 chickens per treatment for the weights recorded. The

dressing percentage (%) and portion yield (%) were calculated as follows:

Dressing percentage (%) = (Cold carcass weight / Live slaughter weight) x 100

Portion yield (%) = (Portion weight / Cold carcass weight) x 100


Experimentally, the study consisted of a randomised factorial block design with six treatments (3

Chicken lines x 2 rearing methods) and n = 50 replications for live slaughter-, carcass-, and portion

weights, yields and percentages calculated. The weekly weights recorded (of all the birds) and

FCR, ADG and EPEF calculated consisted of n = 8 replications for intensive and n = 1 replications


64

for free range, therefore these results were analysed by a completely randomised factorial design.

Since there was only one replication for free range, no standard deviation could be calculated. The

model for the experimental design is indicated by the following equation:

Yijk = µ + βj + bi + gk + (bg)ik + εijk

The terms within the model are defined as: the overall mean (µ), the effect of the block (βj), the

effect of genotype (bi) the effect of rearing method (gk), the effect of the interaction between

chicken genotype and rearing method (bg)ik and εijk is the error associated with the effect of the

block, chicken genotype, rearing method and interaction of the former and the latter. The sensory,

physical and proximate data were subjected to an analysis of variance (ANOVA). The Shapiro-Wilk

test was performed to test for normality (Shapiro & Wilk, 1965). All of the outliers were identified

and removed before final ANOVA`s. The Least Significant Differenced (LSD) was calculated at a

5% significance level to compare the treatment means. Results were defined as being not

significant at P > 0.05 and significant at P ≤ 0.05. SAS™ statistical software (Statistical Analysis

System, Version, 9.2, 2006, SAS Institute Inc., CARY, NC, USA) was used for the analyses of

variance (ANOVA).

RESULTS

Growth parameters, live-, carcass weight and dressing percentage

Growth curves of the three genotypes reared under intensive and free range conditions from day 0

until day 56 are presented in Fig. 4.2. The mean scores and standard deviations (± SD) for ADG,

FCR and EPEF of all the chickens as affected by genotype and production system are presented

in Table 4.2. There was a clear genotype effect (P ≤ 0.05) for ADG and EPEF where broiler scored

higher than hybrid and hybrid higher than Koekoek (Table 4.2). For the FCR, broiler had a better

ratio whilst Koekoek had a weaker ratio.

Production system had no effect on ADG and EPEF however; there was an effect on FCR.

The KFR and HFR chickens had a poorer (P ≤ 0.05) FCR than the KI and HI chickens respectively,

but BI had a poorer (P ≤ 0.05) FCR than the BFR, the latter having the best FCR.

In the intensive production system, the BI were significantly (P ≤ 0.05) heavier (mean ±

s.e.) (2269.8 ± 30.67 g) than the HI (2021.4 ± 35.41 g) which also differed from the KI (1317.0 ±

30.67 g). For the free range birds, the BF had an average live weight of 2144.2 g compared to the

HF’s body weight of 1828.0 g whilst the KF were the lightest (935.6 g).


65

Days

Aver

age

wei

ght p

er c

hick

(g)

BIBFRRKIRKFRKIKFR

0 7 14 21 28 35 42 49 56-200

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

Figure 4.2 Growth curves of three chicken genotypes (broiler, Ross x Potchefstroom Koekoek and

Potchefstroom Koekoek) reared under intensive and free range production systems from

day 0 until slaughtered. (BI – Broiler intensive; BFR – Broiler free range; HI – Ross X

Potchefstroom Koekoek hybrid intensive; HFR – Ross X Potchefstroom Koekoek hybrid

free range; KI – Potchefstroom Koekoek intensive; KFR – Potchefstroom Koekoek free

range)

The mean scores and standard deviations (± SD) for the weight at slaughter, carcass weight and

dressing percentage of the sub-population of chickens selected to be slaughtered as affected by

genotype and production system are presented in Table 4.3. From Table 4.3 and Fig. 4.2 the

chickens from the free range production system within each genotype slaughtered were

significantly larger (live slaughter weight) and had heavier carcasses (P ≤ 0.05) than intensively

reared chickens. Although the free range chickens of each genotype also produced heavier cold

carcasses than intensively reared, this was not significant (P > 0.05). With regards to dressing

percentage, the free range chickens of both the broiler and Hybrid genotypes produced

significantly lower (P ≤ 0.05) dressing percentages than the intensively reared chickens, although

the KFR produced a higher (P ≤ 0.05) dressing percentage than KI.

When considering the genotype difference as a whole for the attributes live slaughter

weight, cold carcass weight and dressing percentage (Table 4.3); broiler scored significantly higher

(P ≤ 0.05) than hybrid, except for live weight where the differences in slaughter weight was not

significant (P > 0.05). The latter scored significantly higher (P ≤ 0.05) than Koekoek for the two

different rearing systems.

BFR

BI

HFR

HI

KI

KFR


66

Portion weight, deboned weight and portion yield

The means and standard deviations (± SD) for the live weight, carcass weight and dressing

percentage of the selected chickens as affected by genotype and production system are presented

in Table 4.4. The chickens were slaughtered at different weights due to sampling bias resulting in

the varying portion weights. The portion weights and deboned weights could thus not be

compared, but rather only percentage yield of the portions will be discussed from here on in.

With regards to the breast yield (%) the broiler was found to be higher (P ≤ 0.05) than that

of the Hybrid and Koekoek. The breasts yield (%) of the broiler and Koekoek reared under free

range production system (BFR 26.0%) were higher (P ≤ 0.05) than that reared in the intensive

production system (BI 25.5%). The HI (23.2%) and KI (21.6%) was significantly higher (P ≤ 0.05)

than HFR (18.9%) and KI (17.1%), but still lower than BI and BFR and higher than KI and KFR for

breast yield.

For thigh yield (%), HFR (14.9%) and KFR (14.6%) scored higher (P ≤ 0.05) yields than HI

(11.7%) and Ki (11.6%). The latter again scored heavier yields (P ≤ 0.05) than BI (10.4%) and

BFR (10.9%) of which, the former and the latter also differed (P ≤ 0.05) from each other.

KFR (9.3%) had the heaviest (P ≤ 0.05) drum yield compared to that produced from all the

other treatments. Also HI (8.2%) and HFR (8.2%) differed (P ≤ 0.05) from BI (7.1%) and BFR

(7.0%) as pertaining to the drum yield.

The wing yield (%) of KFR (7.5%) had a higher (P ≤ 0.05) yield than KI (6.7%), HFR (6.7%)

and HI (5.7%) whilst BI (5.0%) and BFR (5.0%) had the lowest yield (Table 4.4).


67

Table 4.2 The mean scores (± SD) for production parameters of the six chicken treatments as affected by genotype and production system

Broiler Hybrid Koekoek

LSD Intensive Free range Intensive Free range Intensive Free range

FCR 1.78d ± 0.06 1.56d 2.09c ± 0.17 2.43b 2.69b ± 0.15 3.68a 0.29

ADG 53.07a ± 1.82 50.08a 32.27b ± 1.81 31.97b 14.87c ± 1.00 16.22c 3.50

EPEF 284.79a ± 32.94 311.00a 161.78b ± 17.07 134.38b 56.64c ± 6.43 43.88c 49.53

Feed Conversion Ratio (FCR); Average Daily Gain (ADG); European Production Efficiency Factor (EPEF); Standard Deviation(SD); Least Significant Difference (LSD) abMeans in rows with different superscripts are significantly different at P ≤ 0.05

Table 4.3 The mean scores (± SD) for the live weight, carcass weight and dressing percentage of the selected sub-population of the six

chicken treatments (n = 50 per treatment) as affected by genotype and production system



Live slaughter weight (g) 2168.5bc ± 279.79 2331.6a ± 168.45 2101.0c ± 252.45 2250.5ab ± 274.56 1556.4e ± 276.90 1725.2d ± 274.16 101.77

Cold carcass weight (g) 1510.8a ± 213.96 1528.4a ± 128.97 1330.5b ± 182.73 1399.9b ± 181.03 935.2d ± 167.18 1056.1c ± 170.44 69.50

Dressing percentage (%)* 69.7a ± 2.47 65.5b ± 1.89 63.2c ± 2.12 62.17d ± 1.48 59.9f ± 2.05 61.2e ± 1.36 0.76

Standard Deviation (SD); Least Significant Difference (LSD) *Dressing percentage expressed as the relationship between cold carcass weight and live slaughter weight. abMeans in rows with different superscripts are significantly different at P ≤ 0.05


68

Table 4.4 The mean scores (± SD) for the portion weights, portion yields (%) and deboned weights of the six chicken treatments (n = 50 per

treatment) as affected by genotype and production system



Breast (g) 385.4a ± 61.70 396.1a ± 37.42 308.2b ± 263.48 263.5c ± 43.24 227.6d ± 37.66 160.1e ± 30.76 17.18

Breast yield (%)* 25.5b ± 1.19 26.0a ± 1.36 23.2c ± 1.21 18.9e ± 1.35 21.6d ± 0.99 17.1f ± 0.71 0.46

Deboned breast weight (g) 183.8b ± 38.78 210.3a ± 30.06 132.8c ± 23.28 141.5c ± 23.26 94.4d ± 16.84 73.2e ± 16.00 10.19

Thigh (g) 158.3bc ± 25.41 166.5b ± 23.02 156.4c ± 27.93 208.1a ± 14.88 122.4e ± 20.97 136.5d ± 23.76 9.97

Thigh yield (%)* 10.4d ± 0.87 10.9c ± 0.88 11.7b ± 0.85 14.9a ± 0.83 11.6b ± 0.66 14.6a ± 0.86 0.33

Deboned thigh weight (g) 84.6c ± 21.61 101.5a ± 11.30 90.9b ± 14.72 90.5b ± 13.16 68.6d ± 13.43 56.2e ± 12.47 5.84

Drumstick (g) 107.3b ± 15.20 107.5b ± 12.97 108.6ab ± 17.91 114.3a ± 16.30 93.6c ± 18.02 87.6c ± 18.09 6.54

Drumstick yield (%)* 7.1d ± 0.67 7.0d ± 0.66 8.2c ± 0.68 8.2c ± 0.55 8.8b ± 0.63 9.3a ± 0.56 0.25

Deboned drumstick weight (g) 56.1c ± 15.57 64.0b ± 8.25 62.0b ± 9.17 70.1a ± 11.44 54.0c ± 11.49 49.0d ± 11.10 4.49

Wing (g) 76.2b ± 9.19 75.3b ± 7.98 75.5b ± 7.37 92.1a ± 10.94 70.0c ± 12.32 70.4c ± 11.68 4.01

Wing yield (%*) 5.0d ± 0.55 5.0d ± 0.49 5.7c ± 0.63 6.7b ± 0.69 6.7b ± 0.47 7.5a ± 0.52 0.22

Standard Deviation (SD); Least Significant Difference (LSD) *yield expressed as a percentage of cold carcass weight abMeans in rows with different superscripts are significantly different at P ≤ 0.05


69

DISCUSSION

There are many factors such as production system, genotype, age, stocking density, lighting

regime, temperature and diet that may have an effect on the overall production efficiency and yield

of chickens. Therefore this experiment was designed in such a way as to limit the number of

factors to production system and genotype. However, as it is well known that genotype and

production systems affect growth rates, a sub-population of the chickens were thus slaughtered at

different ages but at a fixed weight range to try and compensate for these effects. Growth ADG,

FCR, EPEF, and live- and carcass weight percentage yield of muscle tissue are important

parameters when determining the profitability and feasibility of any system within the chicken

industry.

Effect of genotype

In conventional poultry production, the live weights of birds at slaughter are normally 2 to 2.5 kg,

which results in a 1.3 to1.6 kg carcass weight; this is also applicable to speciality poultry production

(Fanatico et al., 2005). Fast growing broilers reach this market weight in 32 days, while medium

and slower growing birds typically take 63 to 81 days (Gordon & Charles, 2002; Aviagen, 2007). In

this study the broiler chicks (in both production systems) reached this market weight in 42 days

and the Hybrid in 56 days. The Koekoek never reached market weight and were slaughtered on

91 days, with lighter weights. According to Butcher and Nilipour (2009) an average FCR of 1.85,

ADG of 50 g and EPEF of > 260 are required for normal broiler production – no data exists for free

range systems. It is clear from Fig. 4.2 that the broiler was superior (P ≤ 0.05) to the Hybrid and

Koekoek in both production systems, a not so surprising result since this genotype has been

selected for rapid growth over numerous generations. The live slaughter and carcass weights

(Table 4.3) should be interpreted with caution as the data is biased; the BFR of the selected

slaughter birds were heavier than that of the BI although the later had a heavier mean live weight

when the live weights of all the birds were considered. Hybrid was superior (P ≤ 0.05) to Koekoek,

being the medium growing chicken and Koekoek the slower growing genotype. Therefore there

was a clear genotype effect on the FCR, ADG and EPEF as expected (Warriss, 2010). Similar

results were found by Van Marle-Köster and Webb (2000), Fanatico et al. (2005, 2008) and

Bogosavljević-Bosković et al. (2009) where fast growing genotypes were reported to be superior to

medium and slow growing genotypes with regards to growth and weight. Abdullah et al. (2010)

also reported that genotype have an effect on body weight, FCR and ADG.

Although chick behaviour was not quantified, in this study the Koekoek and Hybrid (fast and

medium growing) chicks were observed to be more active in activities like foraging (see Fig 4.3

where no more grass is left in the Koekoek and Hybrid pens (left and right pens) and where grass

is growing high in broiler pens (middle pen), flying, running and venturing outdoors than the broilers


70

(slow growing). Broilers, however, did not forage but rather rested, and were frequently observed

lying down or grouped around feeders and in the shaded area. The fact that the broilers were not

active and did not venture onto the forage area warrants further research as this may have

financial implications as it is commonly believed that chickens prefer foraging and it is then

frequently recommended that free range systems have some foraging pastures available for

welfare reasons. A few leg weaknesses and leg disorders were also observed in the broilers as

well as a higher mortality (Liveability % - BI 95%; BFR 95%; HI 100%; HFR 100%; KI 96.7%; KFR

96.7%) during the experiment, compared to the Hybrid and Koekoek genotypes. Lewis et al.

(1997), Gordon and Charles (2002), Nielsen et al. (2003), Fanantico et al. (2005) and Branciari et

al. (2009) also found that slower growing birds are more active and foraged more than faster

growing birds. Therefore slower growing birds or more active birds are more suitable for an

outdoor production system when pasture is important to the total meat quality. The latter pertains

to the higher n-3 fatty acids that are present in free range meat, these fatty acids originate from the

pasture which contain α-linolenic acid (18:3n3) (Jahan & Paterson, 2007; Ponte et al., 2008).

Higher activity of birds also has a negative effect on the feed efficiency, bringing into account the

production costs in a system that already has higher costs (Fanatico et al., 2005).

Figure 4.3 Image showing the forage (grass) in the Broiler pens (right) and no forage in Hybrid and

Koekoek pens (middle and left).

With regard to the effect of genotype on the carcass composition and portion yield, the following

general trend was observed: medium and slower growing (Hybrid and Koekoek) chickens

produced higher (P ≤ 0.05) yields in the thigh, drumstick and wing whereas faster growing chickens

(broiler) produced higher (P ≤ 0.05) breast yields. This phenomenon could once again be

explained by the fact that the fast growing broiler genotype has been genetically selected for higher

breast yield and thereby decreasing the relative yield of other parts in the body. Alternatively it

could be due the slow and medium growing birds which were noted to have a higher activity, using

their wings and legs more. Gordon and Charles (2002) noted that wing and leg usage is likely to


71

increase bone and supporting muscle mass. These results agree with that reported by Nielsen et

al. (2003, Quentin et al. (2003) and Fanatico et al. (2005). Even though greater (P ≤ 0.05) yields

(%) were found for the Hybrid and Koekoek in the thigh, drumstick and wing compared to than the

broiler, the differences were small and probably not of commercial value. In South Africa the

consumers prefer dark meat (thigh and drumstick) over white meat (breast) (Mankiw & Swagel,

2005). Therefore the HFR would be a better genotype in this production system to meet this

preference. However, Gordon and Charles (2002) reported that the whole (free range produced)

bird may also be vital in the speciality market, since consumers may be looking for the whole bird

cooking/roasting experience.

Although not quantified, it was observed that the Hybrid and Koekoek genotypes had longer

legs than the broilers and as already mentioned the Hybrid thigh and drumstick yields and weights

are heavier than those of the broiler. This aspect warrants further research as the equipment

required to process medium and slow growing birds would need to be adjusted, since these birds

have a larger frame and longer legs than broiler chicken which the equipment is usually set up for

(Fanatico et al., 2005).

Effect of production system

Production system had a significant effect (P < 0.05) on the live weight at slaughter (Fig. 4.2) of the

different genotypes although from Table 4.2 it is interesting to note that the production system had

no effect on ADG within genotype. It was expected that the intensive birds would perform better,

since the free range chickens were more likely to forage and venture outdoors, also other factors

such as temperature and light intensity, which are not controlled and liable to change, may have

affected the growth performance and body weight. For the outdoor chickens to stay warm or

maintain their body temperature they need more metabolise energy than indoor birds, in order to

get more energy they need to consume more feed (increased feed intake). More exercise and

active foraging behaviour are also known to increase feed intake (Fanatico et al., 2008). Although

this experiment was conducted in the summer months (October to January), the birds in the

outdoor (free range) area, even though some did not venture outdoors, were exposed to more

temperature fluctuations than the intensive reared birds. Also interesting to note from the growth

curve (Fig. 4.2) is that KFR not only performed better in live weight gain weight, but also in growth

performance than KI (Table 4.2). There is no explanation for this phenomenon, and further

research is required. Production system also had an effect (P ≤ 0.05) on the dressing percentage

where the free range samples are characterised by lower percentages, except for the genotype

Koekoek where the opposite is true (Table 4.3). A possible reason for the lower dressing

percentage in the free range birds could be due to the intake of grass during foraging, since

dressing percentage is highly correlated to diet (Cerrate et al., 2006). The gastrointestinal tract of

grass feeding chickens will be bigger, therefore resulting in a lower dressing percentage (Castellini

et al., 2002b). Similar results were found by Skomorucha et al. (2009) where indoor birds were


72

characterized by higher dressing percentages. There was also a significant effect of production

system on the FCR, for chicken genotypes (Hybrid and Koekoek) with a higher (P ≤ 0.05) FCR`s

when reared in a free range production system, decreasing the production efficacy of these birds.

Interesting to note is that BFR had a better (P ≤ 0.05) FCR and therefore more economical bird

than BI, which was unexpected since intensive is theoretically production under more ideal

conditions.

Production system also had a significant effect (P ≤ 0.05) on some of the portion yields of

the different genotypes. When broilers were placed in a free range environment their breast and

thigh yield increased (P ≤ 0.05) compared to an intensive environment. While Hybrids were reared

in a free range production system compared to an intensive system the thigh, and wing weight and

yield increased (P ≤ 0.05) whereas breast weight yield decreased (P ≤ 0.05). When Koekoek were

raised in a free range environment breast yield decreased (P ≤ 0.05) while thigh, drumstick and

wing yield increased (P ≤ 0.05). These results could be ascribed to the higher activity of the

outdoor (free range) birds as previously mentioned. This higher activity favoured muscle mass

development, increasing the weight of the muscle and bone (Lewis et al., 1997; Castellini et al.,

2002a; Gordon & Charles 2002). The same results were found by Castellini et al. (2002a) and

Husak et al. (2008) where muscle mass increased when birds were allowed access to an outdoor

environment. The reason for the breast yield not increasing in the HFR chicken samples could be

that the thigh and drumstick was used more in activities like running and grazing, increasing their

weight. Also interesting to note is that the Koekoek also produced higher (P ≤ 0.05) thigh,

drumstick and wing yields and a lower breast yield than the Hybrid when reared in the intensive

production system, but when reared in the free range production system the Hybrid scored higher

yield (P ≤ 0.05) for thigh, drumstick and wing and lower yield for breast (P ≤ 0.05).

CONCLUSIONS

The aim of this study was to perform an explorative study to determine the growth, production

efficiency, carcass and portion yield of the broiler, Hybrid and Potchefstroom Koekoek reared in

intensive and free range production systems. In order to establish if the crossbreeding of broiler

and Potchefstroom Koekoek would affect the morphological and growth properties of a chicken

carcass and if there is any difference, between these treatments.

The results of this study indicate that genotype had a much larger effect than production

system. The intensive broiler and Hybrid birds had a more efficient growth (P ≤ 0.05) than the

respective free range birds From a cost of production view point it would seem that the broiler

have a more efficient (P ≤ 0.05) growth, feed efficiency and meat yield than the Hybrid and

Koekoek genotypes. Despite the poorer growth performance and efficiency (FCR, ADG, and

EPEF) of the medium growing Hybrid birds compared the broiler birds, the former had better

liveability (less mortality), with fewer leg disorders. Further from a behavioural view point, these


73

medium growing birds may be more adapted to a free range production system since they forage

more actively. Additional to these factors, the HFR had higher thigh, drumstick and wing yields

than the broiler. This is beneficial to the industry, since South African consumers prefer dark meat

over white meat. The question arises, whether the consumer is willing to pay a premium price for

free range products to compensate for additional production costs?

It would seem that the Hybrid, when considered for free range rearing, could be a more

suitable alternative than the broiler genotype when evaluated from a morphological yield view

point. Another question that arises is whether the same production efficiency will be maintained if

the study were performed in the winter months, however this still warrants more research?

Another aspect that warrants further research is whether these genotype and production

systems differences, especially as pertaining to the portion yields will result in different meat quality

(chemical composition and sensory quality)? Also, it is not clear what the average South African

consumer would prefer: intensively produced or free range produced?

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Butcher, G.D. & Nilipour, A.H. (2009). Numbers for successful poultry production. [WWW

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carcass and meat quality. Meat Science, 60, 219–225.

Castellini, C., Dal Bosco, A.D., Mugnai, C. & Bernardini, M. (2002b). Performance and behaviour of

chickens with different growing rate reared according to the organic system. Italian Journal

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Dransfield, E. & Soskicki, A. A. (1999). Relationship between muscle growth and poultry meat

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(2008). Performance, liveability, and carcass yield of slow- and fast-growing chicken

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CHAPTER 5

THE INFLUENCE OF REARING SYSTEM AND GENOTYPE ON THE PHYSICAL AND CHEMICAL CHARACTERISTICS OF CHICKEN MEAT

ABSTRACT

Consumer interest in free range poultry production as well as free range produced poultry products

is growing worldwide. In South Africa, little information is available about the effect of this system

on the chemical and physical chicken meat quality. This experiment evaluated the effect of

production system and genotype on the physical characteristics and chemical composition of

chicken meat. Fast growing (Broiler), Slow growing (Potchefstroom Koekoek) and a hybrid

between these two genotypes were reared for 42, 56 and 91 days, respectively before slaughter.

Production system influenced (P ≤ 0.05) the meat pH of the Hybrid and the Broiler. Lower L*, a*,

b*, chroma and higher hue (P ≤ 0.05) values were found in the free range meat samples than the

intensive. Production system caused the free range chickens of the Koekoek to have a higher

(P ≤ 0.05) fat content in the breast and drumstick than in the free range, but in the thigh the

opposite was true. The ash content of the thigh and drumstick were higher (P ≤ 0.05) in Hybrid

intensive and Koekoek intensive than in Hybrid free range and Koekoek free range, respectively.

Higher PUFA:SFA and n-6:n-3 ratios were found in all the free range samples. Koekoek had lower

(P ≤ 0.05) L* values than Broiler and Hybrid. However, the Hybrid had a tendency to score lower

(P ≤ 0.05) for a* and b* values and higher (P ≤ 0.05) for the hue angle than the Broiler and

Koekoek genotypes. Genotype also had small influence on the chemical composition of the

portions where Koekoek had a lower (P ≤ 0.05) moisture content than broiler in the breast but a

higher (P ≤ 0.05) content than broiler and Hybrid in the thigh. Hybrid also had higher (P ≤ 0.05)

protein content than Broiler in the drumstick as well as a higher content (P ≤ 0.05) than broiler and

Koekoek in the breast. Overall, the physical and chemical attributes of the chickens were more

strongly influenced by production system than by genotype, although the quality of the Hybrid meat

was similar to that of the standard commercial Broilers

Keywords: Free range, Broiler, Potchefstroom Koekoek, Ross x Koekoek hybrid, Chemical

composition, Meat quality, Production system, genotype


77

INTRODUCTION

Over the past decade poultry production has shown a rapid incline and dominates the South

African agricultural sector (FAO, 2012; Anon., 2012a). The average South African person

consumes approximately 32.96 kg poultry per annum (Anon., 2012a). This increase in poultry

consumption can be ascribed to higher consumer demand for poultry products as they believe

poultry are healthier and/or cheaper. Modern consumers are more aware of the nutritional value of

the food they consume and wish to be informed of the nutrient composition of food (Sundrum,

2001). Most modern human diets are imbalanced as shown by the rising incidence of lifestyle and

dietary-induced diseases such as depression, cardiocascular diseases, obesity, Type II diabetes

and osteoporosis. A balanced intake of fatty acids (low intake of saturated fatty acids and a high

intake of polyunsaturated and monounsaturated fatty acids) is essential for healthy cell

membranes, normal human development, healthy infant nutrition, mental health in adults, bone

health, healthy skin, strong immunity as well as the the prevention of cancer. Meat is seen as a

major source of fat, especially saturated fatty acids. A high intake of saturated fatty acids and

imbalanced n-6:n-3 ratio are risk factors for humans with coronary heart diseases and

artheosclerosis (Simopoulos, 2002; Gebauer et al., 2006). Poultry meat is a good source of

protein, vitamins, and minerals, has a relatively low fat content and a favourable PUFA to SFA

content which reduces the risk of cardiovascular diseases (Charlton et al., 2008). It is well known

that the chemical and fatty acid content of monogastric animals can be manipulated by the feed

(Wood & Enser, 1997; Fébel et al., 2008).

Consumers are not only more aware of their health and the nutritional value of the food

consumed, but also care more about animal welfare and want more naturally produced products

that support a more sustainable way of farming (Sundrum, 2001). Commercial broilers reared

under controlled environments (often called factory farming) reach market weight in 32 days (2.0

kg). Not only does this rapid growth lead to welfare concerns, but it has been reported that

selection for fast growth and high yield are likely to affect the sensory and functional properties of

chicken meat (Dransfield & Sosnicki, 1999; Le Bihan-Duval et al., 1999). It is possible that

differences in meat quality frequently encountered in the market place may be caused by the

difference in growth rate between fast and slow growing chicken strains/lines (Fanatico et al.,

2005).

Meat quality is to a large extent, influenced by the ultimate pH in the muscle. The pH is an

important characteristic, since it influences amongst other factors the colour, water holding

capacity, juiciness, flavour and microbial shelf life of meat. Chicken genotype and type of muscle

also affects the colour and pH of the meat (Fletcher, 1999; Lawrie & Ledward, 2006). The

nutritional or chemical composition of chicken meat is further influenced by the specific chicken

portion i.e. breast, thigh or drumstick. Therefore, the chemical composition of the major primal cuts

(breast, thigh and drumstick) is an important element in chicken meat quality.


78

A few studies have evaluated the physical characteristics and chemical composition of

fast - , medium- and slow- growing birds, but there is great variation in the production systems,

portion evaluated and type of birds (genotype, strain and age) used (Castellini et al., 2002;

Bogosavljević-Bosković et al., 2006; Grashorn & Serini, 2006; Husak et al., 2008; Ponte et al.,

2008; Wang, 2009; Poltowicz & Doktor, 2011; Fanatico et al., 2005, 2007). Such studies have

never been conducted in a South African environment or on indigenous cross bred (with

commercial Broilers) chickens. Therefore research is needed to evaluate the sustainability of fast-,

medium- and slow- growing genotypes for the South African free range production systems, with

regard to performance, yield, nutritional composition and consumer acceptability. The objective of

this study was to assess the impact of production system and genotype on meat quality and

nutritional composition.

This study evaluated the chemical composition of three different chicken genotypes; Broiler,

Ross X Potchefstroom Koekoek and Potchefstroom Koekoek reared in intensive and free range

environments. The aim of this study was to investigate the effect of chicken genotype (Broiler,

Ross X Koekoek hybrid and Potchefstroom Koekoek) and production system (intensive or free

range) on the physical, chemical and fatty acid composition of the breast, thigh and drumstick.

This study did not include the quantification of the effect of gender (male or female) on chicken

meat quality.



Refer to Chapter 4 for materials and methods on experimental birds, location, handling and

slaughtering procedures of the different chicken treatments.

Experimental units

At the meat science laboratory the carcass was divided into commercial cuts (breast, drumstick,

thigh and wing) with a portioner. First the carcass was cut into half. Then the thighs and

drumsticks were removed from the half carcasses by cutting above the thigh towards the

acetabulum and behind the pubic bone. The thighs and drumsticks were then separated from

each other by cutting perpendicular to the joint between the drumstick and thigh bones. The wings

were removed by cutting the joint between the scapula and the coracoid. Thereafter all the

portions’, except for the wings, skin were removed. The portions were then vacuum-packed and

frozen at -18°C until further analysis. The experimental units included six meat treatments which

consisted of a Broiler, Hybrid and Koekoek sample each reared intensive and free range. An

experimental unit consisted of n = 20 per treatment for physical analysis and n = 10 per treatment

for chemical analysis. The following acronyms are used to describe the six different treatments:


79




Physical analysis

pH

The pH of the breast, thigh and drumstick were measured on the left side of each carcass 2 h post

mortem. The pH was measured by means of a Crison pH 25 hand-held portable pH meter (Lasec

(Pty) Ltd, South Africa) and calibrated before each set of readings with the standard buffers (pH

4.0 and pH 7.0) provided by the manufacturer.

Colour

Samples (n = 20 per treatment) for colour measurement were prepared as described by Honikel

(1998). Each portion was deboned, skinned and bloomed (exposed to atmosphere) at 8°C for 1hr.

The surface colour of the skinless chicken portion was measured at three randomly selected

positions according to the CIELab colour system using a Colour-guide D65/10° (daylight

illumination, aperture opening) 45°/0° colorimeter (Catelogue no. 6805, BYK-Gardner GmbH,

Gerestried, Germany) with L* indicating the lightness, a* the red-green range and b* the blue-

yellow range. The average of the three readings was used in the statistical analysis. The hue

angle (°) and Chroma (C*) were calculated by the use of the individual a* and the b* values

according to the following equations:

Hue-angle (°) = tan-1 (b*/a*)

Chroma (C*) = (a*2 + b*2)-0.5

After the colour readings had been taken, the meat (muscles) of the individual portions were

vacuum packed and stored frozen (-18°C) until chemical analyses could proceed.

Chemical analysis

Sample preparation

The proximate analysis was performed on the uncooked breast, thigh and drumstick muscles of

the chicken (n = 10 per treatment). After the deboned portions were thawed (4°C),

homogenization followed. The samples were re-vacuum packed and frozen (-18°C) until the

proximate analysis commenced when the samples were thawed (4°C) once more. All of the

analysis was performed in duplicate, except for fatty acid analysis.


80

Proximate analysis

The proximate chemical analysis (%) consisted of total moisture, protein, lipid and ash content of

chicken breast, thigh and drumstick muscles. The moisture content (%)(100°C, 24 h) was

analysed by drying a 2.5 g homogenized meat sample according to the Association of Official

Analytical Chemist`s Standard Techniques (AOAC) method 934.01 (AOAC, 2002a). The ash

content (%) (500°C, 6 h) of the moisture free sample was determined by the official AOAC method

942.05 (AOAC, 2002b). The total lipid (%) (intramuscular fat) content of a 5 g homogenised raw

meat sample was determined by using the chloroform:methanol (1:2 v/v) extraction method of Lee

et al. (1996). To determine the total crude protein content (%), a 0.15 g defatted, dried and finely

grounded meat sample was analysed using a Leco Nitrogen/Protein Analyser (FP- 528, Leco

Corporation). The Leco was calibrated with EDTA calibration samples (Leco corporation, 3000

Lakeview Avenue, St. Joseph, MI 49085-2396, USA, Part no. 502-092, Lot no. 1055) before each

of the analysis sessions. The Dumas combustion method 992.15 (AOAC, 2002c) was used and

the results were expressed in % nitrogen (N). The nitrogen (%) was multiplied with the conversion

factor of 6.25 to determine the crude protein (%) present in the meat sample.

Fatty acid analysis

The fatty acid profile of the six meat samples of each treatment was determined by using the fatty

acid methyl esters (FAME) extraction method as described by Folch et al. (1957). A 2 g sample

was extracted by the use of a chloroform:methanol (2:1 v/v) solution. The extraction solvent

contained 0.01% butylated hydroxytoluene (BHT) as an antioxidant. A polytron mixer

(WiggenHauser Homogenizer, D-500 fitted with a standard shaft 1; speed setting D) was used to

homogenise the meat sample with the extraction solvent. Heptadecanoic acid (C17:0) was used

as an internal standard (catalogue number H3500, Sigma-Aldrich Inc., 3050 Spruce Street, St.

Louis, MO 63103, USA) to quantify the individual fatty acids present within the meat sample. A

250 µL sub-sample of the extracted lipids was transmethylated for 2h at 70°C and a

methanol/sulphuric acid (19:1; v/v) solution (2 ml) was used as the transmethylating agent. After

the mixture was cooled to room temperature, extraction of the fatty acid methyl esters (FAME) with

water and hexane followed. The top hexane phase was transferred to a spotting tube and dried

under nitrogen. After drying 50 µL of Hexane were added to the FAME sample, and 1 µL of the

sample was injected into the gas-chromograph (Termo-Electron S.p.A, Rodana, Milan, Italy)

equipped with a 60 m BPX70 capillary column with an internal diameter of 0.25 mm and 0.25 µm

film (SGE International, Ringwood, Victoria, Australia) and flame ionized detector. The gas flow

rate of the carrier, hydrogen, was 30 mL/min. The temperature settings were as follows: initial

temperature 60°C, injector 220°C, detector 260°C and the final temperature at 160°C. The

injection volume was 1 µL with a run time of approximately 45 min. The FAME of the meat

samples was compared to a standard FAME mixture (Supelco™ 37 Component FAME mix C4-


81

C24, CAT, no. 47885-U. Supelco, North Harrison Rd, Bellefonte, PA 16823-0048, USA) to identify

the values. The results were recorded as percentage (%) of the total fatty acids.


Experimentally the study consisted of a randomized factorial block design with six treatments (3

chicken genotypes x 2 production methods) and n = 20 replications for physical measurements,

n = 10 replications for proximate analysis (chosen randomly out of the 20 for physical analysis) and

six replications (randomly chosen out of the 10 replications for proximate analysis) for fatty acid

analysis for portions, breast, thigh and drumstick. The model for the experimental design is

indicated by the following equation:

Yij = µ + βj + bi + gk + (bg)ik + εijk

The terms within the model are defined as; the overall mean (µ), the effect of the block (βj), the

effect of genotype (bi) the effect of rearing method (gk), the effect of the interaction between

chicken genotype and rearing method (bg)ik and εijk is the error associated with the effect of the

block, chicken genotype, rearing method and interaction of the former and the latter. The physical

characteristics and proximate data were subjected to an analysis of variance (ANOVA). The

Shapiro-Wilk test was performed to test for normality (Shapiro & Wilk, 1965). All of the outliers

were identified and removed before final analysis of the ANOVA`s. The Least Significant

Difference (LSD) was calculated at a 5% significance level to compare the treatment means.

Results were defined as being not significant at P > 0.05 and significant at P ≤ 0.05. Correlations

were calculated between the physical characteristics and proximate composition by means of the

Pearson`s correlation coefficient (Snedecor & Cochran, 1980). SAS™ statistical software

(Statistical Analysis System, Version, 9.2, 2006, SAS Institute Inc., CARY, NC, USA) was used for

the analyses of variance (ANOVA).

RESULTS

Physical analysis

pH

The means and standard deviations (± SD) for pH of the breast, thigh and drumstick for the three

different genotypes reared in the two production systems are presented in Table 5.2. No effect for

genotype (P > 0.05) within a production system was found. There were differences (P ≤ 0.05) with

regard to the effect of production system on the Hybrid for the breast, thigh and drumstick portions,


82

where lower (P ≤ 0.05) pH readings were noted in the birds reared in a free range environment.

For Broiler, the birds reared under free range (BFR) conditions, a higher (P ≤ 0.05) pH reading for

the portions thigh and drumstick were measured than for those reared under intensive (BI)

conditions. Although the pH readings for some of the treatments differed statistically, they were of

a smaller magnitude (< 0.2 pH units) indicating that the samples were very similar.

Table 5.2 The mean scores (± SD) for the pH of the breast, thigh and drumstick of chicken as

affected by genotype and production system

pH Broiler Hybrid Koekoek

LSD Intensive Free Range Intensive Free Range Intensive Free Range

Breast 5.92b ± 5.94 5.93ab ± 0.21 6.08a ± 0.30 5.89b ± 0.27 5.92b ± 0.21 5.93ab ± 0.17 0.15

Thigh 6.16b ± 0.18 6.32a ± 0.12 6.28a ± 0.16 6.09b ± 0.16 6.30a ± 0.16 6.31a ± 0.10 0.10

Drumstick 6.27cd ± 0.20 6.41ab ± 0.11 6.47a ± 0.15 6.18d ± 0.19 6.34bc ± 0.16 6.31bc ± 0.12 0.10

Standard Deviation (SD); Least Significant Difference (LSD) abMeans in rows with different superscripts are significantly different at P ≤ 0.05

Colour

The means and standard deviations (± SD) for the colour coordinates (L*, a* and b*), the

calculated hue angle (°) and Chroma (C*) for the six different treatments as affected by genotype

and production system are presented in Table 5.3.

According to Table 5.3 there was an effect of production system within a genotype on the

L* coordinate for all the portions where the BFR and KFR differed (P ≤ 0.05) and was darker in

colour (lower L* value) than the respective intensive (BI and KI) breast samples. For the thigh and

drumstick portions, KFR (P ≤ 0.05) had a lower L* value and was therefore darker in colour than KI

and all the other samples. The HI and HFR did not differ (P > 0.05) from each other for all the

portions as pertaining to the L* value. There was a trend that the free range samples of each

genotype showed a more green (lower a* value) and blue (lower b* value) colour, some of these

differences were significant (P ≤ 0.05) and some not (P > 0.05) in all the portions (Table 5.3). Hue

angle (°) and chroma (C*) give a more comprehensive, three-dimensional view of the colour of

meat. Production system also had an effect (P ≤ 0.05) on the hue and chroma values within a

genotype for the portions breast, thigh and drumstick. The free range sample of each genotype

had lower (P ≤ 0.05) chroma values than the intensive samples. Considering the hue angle, all the

free range treatments had significantly higher (P ≤ 0.05) values, except for Broiler breast, where

free range had a lower hue (P ≤ 0.05) value and Broiler drumstick, where no difference (P > 0.05)

was detected.

For the effect of genotype within a production system, the Koekoek genotype had the

lowest L* (darker in colour) (P ≤ 0.05) value for portions thigh and drumstick than Hybrid and

Broiler, the latter two however, did not differ (P > 0.05) from each other. There was also a

tendency for the Hybrid and Koekoek to be a more green (lower a* value) and blue (lower b* value)


83

colour (P ≤ 0.05) than Broiler. Regarding the hue value, it would seem that the hybrid within each

respective production system had a higher value than Broiler and Koekoek genotypes. The hue

angle of the former and the latter did not differ (P ≤ 0.05) from each other in the breast, thigh and

drumstick portions. For chroma, the broiler had higher values (P ≤ 0.05) than the other genotypes

within a specific production system for every portion. For the breast meat, the KI sample had a

lower (P ≤ 0.05) chroma value than the other genotypes for that same production system. It would

seem that for colour the effect of production system was more pronounced than the effect of

genotype.

Table 5.3 The mean scores (± SD) for the CIE L*a*b*, hue and chroma values of the breast, thigh

and drumstick of chicken meat as affected by genotype and production system


LSD Intensive Free range Intensive Extensive Intensive Extensive

Breast

CIE L* 56.8a ± 2.02 55.1b ± 1.74 57.0a ± 1.57 55.6ab ± 3.85 57.0a ± 1.98 51.0c ± 1.49 1.44

CIE a* 3.7a ± 0.85 3.2a ± 1.19 1.8b ± 1.01 -1.1c ± 1.59 2.1b ± 1.32 -0.6c ± 0.95 0.74

CIE b* 14.7b ± 2.15 11.2cd ± 2.25 12.2bc ± 1.74 9.4e ± 2.52 13.1b ± 2.65 9.9ed ± 2.00 1.41

Hue 75.4d ± 3.03 73.1b ± 6.03 80.9c ± 5.06 98.6a ± 11.16 79.7c ± 6.20 92.7b ± 5.36 4.22

Chroma 15.3a ± 1.98 11.4c ± 1.65 12.5bc ± 1.78 9.7d ± 2.44 13.4b ± 2.51 10.0d ± 2.03 1.32

Thigh

CIE L* 56.0a ± 1.81 55.4a ± 1.46 55.4a ± 2.85 54.8a ± 2.52 53.2b ± 1.20 49.7c ± 1.67 2.21

CIE a* 5.5a ± 1.18 3.5b ± 1.03 4.0b ± 1.40 0.6d ± 2.31 5.3a ± 1.34 1.6c ± 1.10 1.03

CIE b* 14.4a ± 1.89 11.9bc ± 1.76 12.3b ± 1.67 10.0d ± 2.91 12.0bc ± 1.98 10.8cd ± 1.85 1.41

Hue 68.4de ± 5.11 73.4c ± 5.00 71.6cd ± 7.18 87.8a ± 12.23 64.8e ± 7.07 81.6b ± 5.92 1.98

Chroma 15.69a ± 1.77 12.5b ± 1.74 13.2b ± 1.42 10.4c ± 3.03 13.2b ± 1.42 11.1c ± 1.82 1.46

Drumstick

CIE L* 56.9a ± 3.54 56.5a ± 2.24 57.4a ± 4.70 58.1a ± 4.44 54.4b ± 2.70 52.2c ± 2.66 1.33

CIE a* 5.3ab ± 1.53 5.1ab ± 1.15 4.5b ± 1.92 1.1c ± 2.20 5.8a ± 1.38 1.9c ± 1.40 1.98

CIE b* 13.6a ± 2.25 11.2b ± 1.92 10.3bc ± 2.91 9.8c ± 2.56 10.0bc ± 1.60 9.1c ± 1.83 1.98

Hue 66.8c ± 8.93 64.3cd ± 7.34 65.2c ± 9.72 83.9a ± 12.33 58.7d ± 6.50 77.5b ± 8.45 4.72

Chroma 15.6a ± 2.91 12.6b ± 1.69 11.7b ± 2.68 10.2c ± 2.77 9.6b ± 1.76 9.6c ± 1.77 1.98


Proximate analysis

The proximate analysis results (means and standard deviations (± SD) expressed as g/100 g

meat) of the raw breast, thigh and drumstick meat samples as affected by genotype and production

system are depicted in Table 5.4. In all the portions, moisture was the highest, followed by protein,

fat and then ash. In general the chemical composition of the three different portions and of the

different treatments did not differ greatly.


84

Rearing system influenced some of the components of the chemical composition of the

breast, thigh and drumstick portions (P ≤ 0.05). Rearing chickens in a free range environment only

influenced the protein content of the Broiler, where BFR (21.3 g/100 g) had significantly higher

concentrations (P ≤ 0.05) than BI (22.1 g/100 g) and the fat content of the Koekoek, where KFR

(3.1 g/100 g) had lower (P ≤ 0.05) concentrations than KI (3.6 g/100 g) in the breast sample.

Rearing the Hybrid in a free range environment caused the breast meat to have a lower protein

content than in an intensive (P ≤ 0.05) environment (HFR: 22.5 g/100 g; HI 23.3g /100g). In the

thigh meat, there was no production system effect on the Broiler samples (P > 0.05), however

there were effects on the ash content of the Hybrid hybrid (HI 1.1 g/100 g; HFR 1.2g/100 g) and on

the protein (KI 18.6 g/100 g; KFR 15.5 g/100 g) and fat (KI 8.3 g/100 g; KFR 12.1 g/100 g) contents

of the Koekoek samples. Regarding the composition of the drumstick meat, production system

had significant effects on the moisture and ash contents of the Koekoek and Hybrid hybrid samples

respectively. Production system also had a significant effect on the fat content of the drumstick for

genotypes Broiler and Koekoek, where intensive (BI 5.3 g/100g; KI 5.1 g/100g) had higher

(P ≤ 0.05) concentrations than free range (BFR 3.6 g/100 g; KFR 3.8 g/100g).

With regards to the effect of genotype, no differences were found for ash in the breast,

although the ash content of the thigh and drumstick portions differed, however these were of small

magnitude. Genotype had an effect on the breast and thigh portions where Koekoek had a lower

(P ≤ 0.05) moisture content than Broiler, but were similar to Hybrid (P > 0.05) in the breast, but in

the thigh Broiler had a lower (P ≤ 0.05) moisture content than Koekoek and Hybrid, the former and

the latter did not differ from each other (P > 0.05). With regards to the fat content, genotype had

an effect on the thigh and the breast meat samples where Koekoek had a higher (P ≤ 0.05) content

than Broiler in the breast although in the thigh the opposite were true. Hybrid did not differ

(P > 0.05) from either Broiler or Koekoek for fat content. The Hybrid had a higher (P ≤ 0.05)

protein content than the Broiler and Koekoek genotypes, although the Broiler and Koekoek

genotypes did not differ from each other (P > 0.05). For the drumstick meat, Hybrid and Koekoek,

which did not differ (P > 0.05) from each other, had a higher (P ≤ 0.05) protein content than Broiler.

Genotype did not have any effect (P > 0.05) on protein content of the thigh meat. Although there

were statistically significant differences in the effects of genotype and production system, all these

values fall within the standard nutritional value of chicken meat.


85

Table 5.4 The mean scores (± SD) for the proximate composition (g/100 g as is) of raw chicken

breast, thigh and drumstick as affected by genotype and production system



Breast

Moisture 74.0a ± 0.78 73.4a ± 0.52 71.8c ± 0.31 72.0c ± 0.56 72.3bc ± 0.64 72.7b ± 0.77 0.55

Protein 22.1bc ± 0.63 21.3d ± 1.12 23.3a ± 0.65 22.5b ± 0.52 21.5cd ± 1.16 21.4cd ± 0.65 0.74

Fat 3.0b ± 0.29 2.8b ± 0.65 2.3c ± 0.48 2.7bc ± 0.62 3.6a ± 0.39 3.1bc ± 0.53 0.46

Ash 1.2 ± 0.11 1.2 ± 0.05 1.2 ± 0.06 1.1 ± 0.06 1.2 ± 0.16 1.2 ± 0.06 0.08

Thigh

Moisture 68.5c ± 2.03 69.1bc ± 1.48 69.1bc ± 2.2 70.1abc ± 1.6 71.7a ± 2.6 70.9ab ± 2.0 1.81

Protein 17.9ab ± 4.91 16.4abc ± 1.67 17.8ab ± 0.95 16.1bc ± 1.60 18.6a ± 2.06 15.5c ± 1.63 2.23

Fat 12.9a ± 4.55 12.9a ± 2.47 11.8a ± 2.48 12.4a ± 2.30 8.3b ± 1.44 12.1a ± 2.48 2.50

Ash 1.0bc ± 0.08 1.0bc ± 0.03 1.1b ± 0.09 1.2a ± 0.2 1.0c ± 0.04 1.1bc ± 0.06 0.09

Drumstick

Moisture 75.3a ± 0.58 75.3a ± 0.58 74.8a ± 0.56 75.0a ± 0.46 74.0b ± 0.68 74.8a ± 0.56 0.58

Protein 16.6c ± 1.22 17.3bc ± 0.81 18.2a ± 0.72 17.5ab ± 0.46 17.6ab ± 0.56 18.2a ± 0.61 0.69

Fat 5.3a ± 0.47 3.6d ± 0.29 4.1bc ± 0.50 4.3b ± 0.47 5.1a ± 0.47 3.8dc ± 0.26 0.38

Ash 1.1a ± 0.5 1.1a ± 0.03 1.1a ± 0.06 1.0b ± 0.07 1.1a ± 0.11 1.1a ± 0.05 0.06


Fatty acid analysis

The mean percentages and standard deviations (± SD) for the fatty acid composition of the raw

breast, thigh and drumstick meat of the six different treatments are presented in Table 5.5, 5.6 and

5.7 respectively. All of the fatty acids present in the treatments were analysed and are presented

in the table although only specific fatty acids will be discussed. In general the fatty acid

composition of the three different portions and of the different treatments did not differ greatly. The

concentration of total polyunsaturated fatty acid (PUFA) is the highest, followed by total saturated

fatty acid (SFA) and then total monounsaturated fatty acid (MUFA) in all the chicken samples

irrespective of genotype or portion (Table 5.5, 5.6 and 5.7).

When considering the overall SFA (Table 5.5) content of the breast meat, there is a

production system effect in the Hybrid and Broiler samples, where the intensive production system

(HI 33.3%; BI 35.9%) had a higher (P ≤ 0.05) total SFA content than free range production system

(HFR 28.8%; BFR 29.8%), although the SFA content of KI was higher than KFR, this was not

significant (P > 0.05). As pertaining to production system, there was a difference (P ≤ 0.05)

between BI (24.0%), HI (21.7%), KI (21.0%) and BFR (18.1%), HFR (18.9%), KFR (18.6%)

respectively for Palmitic acid (C16:0) where intensive had a higher (P ≤ 0.05) percentage than free

range. There were also differences (P ≤ 0.05) between production systems within a genotype for

Stearic acid (C18:0) where HI (9.9%) had higher values than HFR (8.3%). For the thigh meat


86

(Table 5.6), there was no production system effect (P > 0.05) with regards to the total SFA. As

pertaining to the individual SFA of the thigh, Stearic acid differed (P ≤ 0.05) for Broiler between BI

(3.2%), with a higher content than BFR (2.4%). The total SFA content of the drumstick meat

(Table 5.7) was also influenced by the production system where the free range samples had lower

(P ≤ 0.05) sums of SFA than the intensive samples, except HI and HFR whose sums did not differ

(P > 0.05). Of the individual fatty acids, Palmitic acid and Stearic acid differed significantly

between production systems for the Broiler and Koekoek genotypes, where the intensive had

higher (P ≤ 0.05) percentages than the free range.

The total MUFA content of the breast, thigh and drumstick meat differed between

production systems for the Broiler and Koekoek genotypes, where the intensive reared genotypes

had the higher (P ≤ 0.05) MUFA. When considering the individual fatty acids, Palmitoleic acid

(C16:1) and Oleic acid (C18:1n9c) were the major fatty acids that differed. In the breast meat,

higher concentrations (P ≤ 0.05) were found in the intensive samples BI and KI than in the free

range samples BFR and KFR, respectively. The BI had higher (P ≤ 0.05) levels of Palmitoleic and

Oleic than BFR in the thigh meat. As pertaining to the drumstick meat, intensive reared broilers

(BI) had higher (P ≤ 0.05) concentrations of these two fatty acids than free range reared broilers

(BFR).

In the total PUFA content of the breast, thigh and drumstick, there were a trend for the free

range samples to have higher concentrations than the intensive. Linolenic acid (C18:2n6c) and L-

Linolenic acid (C18:3n6) were the major PUFA present. In the breast meat, free range rearing had

a significant effect and the BFR (36.3%; 4.6%), HFR (36.1%; 4.6%), KFR (38.6%; 4.5%) had

higher (P ≤ 0.05) Linolenic acid and L-Linolenic acid concentrations than the respective intensive

samples, BI (23.1%; 2.6%), HI (31.5%; 3.4%) and KI (33.4%; 3.6%). In the thigh meat, the Broiler

genotype had a higher (P ≤ 0.05) Linolenic acid concentration when reared under free range

conditions. With regards to the drumstick meat, BFR and KFR had higher Linolenic acid

concentrations and HFR higher L-Linolenic acid concentrations than the respective intensive

samples.

Considering the overall PUFA:SFA ratio, there seemed to be a trend for free range samples

to have higher ratios than intensive, except for the Hybrid genotype in the drumstick meat, where

HI had a higher (P ≤ 0.05) ratio than HFR. The n-3:n-6 fatty acid ratio was lower (P ≤ 0.05) in the

intensive samples of the broiler (BI) genotype for breast, thigh and drumstick portions and also

lower for the thigh and drumstick portions derived from KI. There were also significant (P ≤ 0.05)

differences in all the portions for the effect of production system within a specific genotype, for the

remainder fatty acids, but these were very small, with differences < 1.0% and are therefore not

discussed further.

It is clear from Tables 5.5, 5.6 and 5.7 that production system had a larger effect than

genotype on the fatty acid profile of the different portions.


87

Table 5.5 The mean concentrations (± SD) of the fatty acid composition (% of total fatty acids) of

raw chicken breast as affected by genotype and production system

Fatty acid Broiler Hybrid Koekoek


SFA C14:0 0.4ab ± 0.14 0.3bc ± 0.07 0.4a ± 0.43 0.3c ± 0.07 0.4ab ± 0.10 0.3bc ± 0.08 0.12

C15:0 0.1b ± 0.01 0.1ab ± 0.01 0.1a ± 0.02 0.1ab ± 0.02 0.1a ± 0.02 0.1a ± 0.02 0.02

C16:0 24.0a ± 2.70 18.1d ± 0.94 21.7b ± 0.81 18.9dc ± 2.63 21.0bc ± 2.08 18.6d ± 1.21 2.30

C18:0 10.0a ± 0.42 9.9a ± 1.46 9.9a ± 1.24 8.3b ± 0.65 9.9a ± 1.18 9.6a ± 0.67 1.26

C20:0 0.2b ± 0.09 0.3ab ± 0.09 0.3ab ± 0.10 0.4a ± 0.09 0.3b ± 0.09 0.2b ± 0.03 0.10

C21:0 0.1a ± 0.01 0.1b ± 0.01 0.1ab ± 0.02 0.1a ± 0.01 0.1ab ± 0.02 0.00ab ± 0.01 0.02

C22:0 1.0a ± 0.14 1.0a ± 0.25 0.8ab ± 0.14 0.8bc ± 0.10 0.5d ± 0.08 0.6cd ± 0.10 0.19

C24:0 0.1b ± 0.02 0.1a ± 0.02 ND ND ND ND 0.02

MUFA

C14:1 0.0a ± 0.02 0.0ab ± 0.02 ND ND 0.0b ± 0.02 ND 0.02

C16:1 3.1a ± 0.38 1.3dc ± 0.38 2.1b ± 0.63 1.4bc ± 0.78 1.5bc ± 0.43 0.8d ± 0.13 0.63

C18:1n9t 0.2a ± 0.03 0.1c ± 0.01 0.1b ± 0.01 0.1cd ± 0.03 0.1c ± 0.02 0.1d ± 0.00 0.02

C18:1n9c 27.8a ± 1.75 21.3bc ± 1.75 23.0b ± 2.15 22.2bc ± 1.76 23.1b ± 1.67 20.4c ± 0.57 1.98

C20:1 0.1c ± 0.01 0.1ab ± 0.01 0.1b ± 0.01 0.1ab ± 0.1 0.1b ± 0.01 0.1a ± 0.01 0.01

C22:1n9 0.1b ± 0.01 0.1a ± 0.02 0.1b ± 0.01 0.1b ± 0.02 0.0c ± 0.01 0.0c ± 0.01 0.02

C24:1 0.1b ± 0.03 0.1abc ± 0.03 0.1ab ± 0.03 0.1bc ± 0.02 0.1bc ± 0.02 0.1c ± 0.02 0.03

PUFA

C18:2n6t 0.1ab ± 0.01 0.1ab ± 0.00 0.1ab ± 0.01 0.1a ± 0.00 0.1ab ± 0.02 0.1b ± 0.01 0.01

C18:2n6c 23.1d ± 1.71 36.3ab ± 2.45 31.5c ± 1.91 36.1ab ± 3.88 33.4bc ± 2.54 38.6a ± 2.27 3.31

C18:3n6 2.6c ± 0.29 4.6a ± 0.42 3.4b ± 0.38 4.6a ± 0.68 3.6b ± 0.43 4.5a ± 0.36 0.55

C18:3n3 0.5a ± 0.05 0.3bc ± 0.03 0.4b ± 0.05 0.3b ± 0.04 0.4b ± 0.04 0.3c ± 0.03 0.05

C20:2 0.4b ± 0.10 0.6a ± 0.15 0.4b ± 0.07 0.4b ± 0.08 0.3c ± 0.04 0.3bc ± 0.03 0.11

C20:3n6 2.1b ± 0.26 3.0a ± 0.97 3.1a ± 1.07 2.8ab ± 0.43 2.7ab ± 0.68 3.5a ± 0.69 0.92

C20:3n3 0.1 ± 0.00 0.1 ± 0.02 0.1 ± 0.02 0.1 ± 0.01 0.1 ± 0.02 0.1 ± 0.01 0.02

C20:4n6 0.1a ± 0.02 0.1ab ± 0.02 0.1ab ± 0.02 0.1ab ± 0.01 0.0b ± 0.01 0.0b ± 0.01 0.02

C20:5n3 0.2b ± 0.04 0.3a ± 0.07 0.2b ± 0.03 0.2ab ± 0.03 0.2b ± 0.05 0.2b ± 0.02 0.06

C22:2 0.0a ± 0.01 0.1a ± 0.02 ND ND ND ND 0.01

C22:5n3 0.5a ± 0.09 0.2b ± 0.05 0.2b ± 0.03 0.2b ± 0.02 0.1c ± 0.02 0.1c ± 0.01 0.05

C22:6n3 2.0a ± 0.42 1.0cd ± 0.34 1.5b ± 0.30 1.2bc ± 0.26 1.0d ± 0.24 1.4bc ± 0.30 0.38

SFA 35.9a ± 2.52 29.8cd ± 1.88 33.3ab ± 1.87 28.8d ± 3.00 32.2cb ± 3.10 29.5cd ± 1.86 2.99

MUFA 31.3a ± 1.40 23.4bc ± 2.43 25.7b ± 2.91 23.9bc ± 2.47 24.8b ± 2.03 21.4c ± 0.63 2.66

PUFA 32.2c ± 2.85 46.6a ± 62 40.8b ± 2.14 47.2a ± 4.97 42.5b ± 3.33 48.7a ± 1.96 4.03

PUFA:SFA 0.9c ± 0.13 1.6ab ± 0.16 1.2c ± 0.10 1.6ab ± 0.26 1.3bc ± 0.22 1.6a ± 0.17 0.24

n-6:n-3 9.5c ± 1.56 21.6a ± 4.44 16.7b ± 2.67 20.4ab ± 2.06 23.4a ± 4.16 23.5a ± 4.28 4.33

Standard Deviation (SD); Least Significant Difference (LSD); Not Detected (ND) abMeans in rows with different superscripts are significantly different at P ≤ 0.05


88


raw chicken thigh as affected by genotype and production system



SFA C14:0 0.2a ± 0.10 0.1dc

± 0.04 0.2ab ± 0.04 0.2abc ± 0.05 0.1bcd ± 0.03 0.1d ± 0.02 0.07

C15:0 0.1a ± 0.04 0.0b ± 0.01 0.0b ± 0.01 0.0b ± 0.01 0.0b ± 0.02 0.0b ± 0.01 0.02

C16:0 14.4ab ± 7.54 11.2ab ± 8.76 10.4ab ± 4.16 8.0b ± 1.76 15.8a ± 7.29 11.1ab ± 6.01 2.04

C18:0 3.2a ± 0.23 2.4bc ± 0.68 2.4bc ± 0.6 2.8ab ± 0.4 2.2bc ± 0.55 2.0c ± 0.45 0.68

C20:0 0.2a ± 0.10 0.1bc ± 0.05 0.2abc ± 0.09 0.2ab ± 0.09 0.1abc ± 0.11 0.1c ± 0.03 0.10

C21:0 0.1 ± 0.02 ND ND ND ND ND 0.01

C22:0 0.5a ± 0.26 0.2b ± 0.04 0.1b ± 0.03 0.2b ± 0.04 0.1b ± 0.03 0.1b ± 0.02 0.13

C24:0 ND ND ND ND ND ND 2.04

MUFA C14:1 0.1a ± 0.02 ND ND ND ND ND 0.01

C16:1 1.3a ± 0.07 0.6bc ± 0.15 1.3a ± 0.19 0.8b ± 0.19 0.7bc ± 0.20 0.5c ± 0.20 0.26

C18:1n9t 0.1a ± 0.03 0.0bc ± 0.01 0.0b ± 0.01 0.0bc ± 0.01 0.0bc ± 0.01 0.0c ± 0.01 0.02

C18:1n9c 31.6a ± 8.39 19.3bc ± 12.06 20.1bc ± 11.50 10.4c ± 1.81 25.0ab ± 8.15 18.3bc ± 9.03 2.04

C20:1 0.1a ± 0.03 0.0b ± 0.01 0.0b ± 0.01 0.0b ± 0.01 ND 0.0b ± 0.01 0.02

C22:1n9 0.1c ± 0.02 0.0c ± 0.01 0.0c ± 0.01 0.0c ± 0.01 0.5a ± 0.18 0.3b ± 0.21 0.16

C24:1 0.1 ± 0.02 ND ND ND ND ND 0.01

PUFA C18:2n6t ND ND ND ND ND ND 0.01

C18:2n6c 37.9c ± 13.21 63.2ab ± 12.58 60.2ab ± 15.48 73.2a ± 4.80 53.3b ± 13.00 65.1ab ± 13.75 2.04

C18:3n6 2.3a ± 0.98 1.8ab ± 0.31 1.7ab ± 0.45 2.3a ± 0.08 1.2b ± 0.38 1.7b ± 0.27 0.62

C18:3n3 0.3a ± 0.16 0.1b ± 0.02 0.2b ± 0.04 0.1b ± 0.03 0.1b ± 0.03 0.1b ± 0.02 0.09

C20:2 0.2a ± 0.13 0.1b ± 0.02 0.1b ± 0.03 0.1b ± 0.02 0.1b ± 0.02 0.1b ± 0.01 0.07

C20:3n6 1.5a ± 0.90 0.4b ± 0.14 0.4b ± 0.09 0.6b ± 0.12 0.4b ± 0.15 0.3b ± 0.15 0.47

C20:3n3 0.1a ± 0.01 ND ND ND ND ND 0.01

C20:4n6 ND 0.0b ± 0.1 0.0ab ± 0.01 ND 0.0a ± 0.01 ND 2.04

C20:5n3 0.2a ± 0.07 0.0b ± 0.01 0.0b ± 0.01 0.1b ± 0.01 0.0b ± 0.01 0.0b ± 0.01 0.03

C22:2 ND ND ND ND ND ND 2.04

C22:5n3 0.1a ± 0.01 0.0b ± 0.01 0.0b ± 0.02 0.1b ± 0.01 0.0c ± 0.01 0.0c ± 0.01 0.02

C22:6n3 0.8a ± 0.42 0.1b ± 0.05 0.2b ± 0.05 0.2b ± 0.04 0.1b ± 0.06 0.1b ± 0.04 0.20

SFA 21.7a ± 11.22 14.1ab ± 8.90 14.3ab ± 5.69 11.4b ± 2.20 18.4ab ± 6.64 13.4ab ± 5.50 2.04

MUFA 34.5a ± 7.85 20.1bc ± 11.91 21.9bc ± 11.63 11.6c ± 2.35 26.2ab ± 7.95 19.1bc ± 8.81 2.04

PUFA 43.6c ± 11.05 65.8ab ± 13.11 63.8bc ± 14.75 76.9a ± 4.52 55.4bc ± 13.60 67.5ab ± 14.10 2.04

PUFA:SFA 2.8c ± 1.89 6.3ab ± 3.24 5.1abc ± 2.26 7.0a ± 1.83 3.8bc ± 2.63 6.1ab ± 3.35 2.04

n-6:n-3 35.3d ± 25.73 216.8ab ± 20.66 162.3c ± 17.24 171.2c ± 39.83 186.0bc ± 29.68 242.4a ± 36.58 35.71



89


raw chicken drumstick as affected by genotype and production system



SFA

C14:0 0.3ab ± 0.16 0.1c ± 0.04 0.4a ± 0.12 0.4ab ± 0.08 0.3ab ± 0.06 0.2bc ± 0.13 0.13

C15:0 0.1ab ± 0.04 0.0c ± 0.01 0.1a ± 0.03 0.1a ± 0.02 0.1a ± 0.02 0.1bc ± 0.03 0.03

C16:0 17.2a ± 7.00 7.0b ± 1.88 17.1a ± 5.01 18.1a ± 1.29 17.9a ± 1.67 8.0b ± 1.51 4.59

C18:0 5.3b ± 2.44 3.0c ± 0.88 7.7a ± 1.96 8.4a ± 0.48 8.5a ± 0.38 4.4bc ± 1.80 1.88

C20:0 0.2b ± 0.10 0.2 a± 0.08 0.3b ± .011 0.4a ± 0.04 0.3a ± 0.09 0.2b ± 0.07 0.1

C21:0 0.0a ± 0.02 0.0b ± 0.01 0.0a ± 0.02 0.1a ± 0.02 0.1a ± 0.02 0.0b ± 0.01 0.02

C22:0 0.5b ± 0.23 0.3c ± 0.09 0.5b ± 0.12 0.7a ± 0.08 0.7a ± 0.09 0.2c ± 0.12 0.16

C24:0 0.0b ± 0.02 0.0c ± 0.00 ND ND 0.1a ± 0.1 ND 0.01

MUFA

C14:1 0.1a ± 0.03 0.0d ± 0.01 0.1ab ± 0.02 0.0ab ± 0.01 0.0bc ± 0.01 0.0cd ± 0.01 0.02

C16:1 3.0a ± 1.23 0.8c ± 0.26 2.6a ± 0.98 2.1ab ± 0.63 2.0ab ± 0.83 1.4bc ± 0.76 1.00

C18:1n9t 0.1a ± 0.04 0.0b ± 0.01 0.1a ± 0.03 0.1a ± 0.02 0.1a ± 0.01 0.0b ± 0.01 0.03

C18:1n9c 36.4a ± 9.08 10.4c ± 3.01 21.9b ± 5.80 21.8b ± 1.77 21.4b ± 1.69 15.7b ± 6.93 6.66

C20:1 0.0b ± 0.02 0.0b ± 0.01 0.1a ± 0.02 0.1a ± 0.01 0.1a ± 0.01 0.1b ± 0.02 0.02

C22:1n9 0.0b ± 0.02 0.0b ± 0.01 0.0b ± 0.01 0.1a ± 0.01 0.1a ± 0.01 0.0c ± 0.00 0.01

C24:1 0.1b ± 0.02 0.0c ± 0.01 0.1ab ± 0.02 0.1a ± 0.01 0.1a ± 0.01 0.0c ± 0.02 0.02

PUFA

C18:2n6t 0.0c ±0.01 0.0c ± 0.00 0.1b ± 0.01 0.1a ± 0.01 0.1a ± 0.01 0.0c ± 0.01 0.01

C18:2n6c 32.3b ± 7.11 74.0a ± 6.17 34.1b ± 2.89 38.1b ± 3.45 38.4b ± 3.92 68.8a ± 5.64 6.44

C18:3n6 0.4c ± 1.17 2.4c ± 0.44 3.6b ± 0.84 4.7a ± 0.52 4.8ab ± 0.58 1.9c ± 0.45 0.89

C18:3n3 0.3a ± 0.15 0.1b ± 0.03 0.4a ± 0.09 0.3a ± 0.02 0.3a ± 0.03 0.2b ± 0.09 0.10

C20:2 0.2c ± 0.09 0.2c ± 0.04 0.3b ± 0.07 0.4a ± 0.05 0.4a ± 0.05 0.2c ± 0.07 0.08

C20:3n6 0.9b ± 0.52 0.8b ± 0.24 2.5a ± 0.28 2.8a ± 0.31 2.9a ± 0.35 1.0b ± 0.28 0.43

C20:3n3 0.0c ± 0.01 0.0c ± 0.01 0.1b ± 0.02 0.1a ± 0.01 0.1ab ± 0.00 0.0c ± 0.01 0.01

C20:4n6 0.0a ± 0.02 0.0b ± 0.01 0.1a ± 0.02 0.1a ± 0.01 0.1a ± 0.01 0.0b ± 0.00 0.02

C20:5n3 0.1b ± 0.05 0.1b ± 0.03 0.2b ± 0.05 0.2a ± 0.04 0.2a ± 0.04 0.1b ± 0.06 0.05

C22:2 0.0b ± 0.01 0.0c ± 0.00 ND ND 0.0a ± 0.01 ND 0.01

C22:5n3 0.2a ± 0.10 0.1c ± 0.02 0.1c ± 0.03 0.2b ± 0.02 0.2b ± 0.02 0.1c ± 0.04 0.05

C22:6n3 0.6a ± 0.32 0.3b ± 0.06 0.8a ± 0.17 0.8a ± 0.07 0.8a ± 0.08 0.3b ± 0.19 0.21

SFA 26.5a ± 10.51 10.6b ± 2.86 26.8a ± 6.82 28.0a ± 1.65 27.9a ± 1.94 14.9b ± 6.63 7.31

MUFA 39.7a ± 8.01 11.3d ± 3.21 25.2b ± 7.16 24.2b ± 2.37 23.7bc ± 2.47 17.2cd ± 7.37 6.88

PUFA 33.0d ± 12.47 77.9a ± 5.54 42.4cd ± 3.45 47.6c ± 3.81 48.2c ± 4.21 67.6b ± 12.97 10.23

PUFA:SFA 1.7c ± 1.26 7.8a ± 2.02 2.2c ± 1.81 1.7c ± 0.23 1.7c ± 0.25 5.3b ± 2.06 1.82

n-6:n-3 26.8b ± 16.85 132.9a ± 28.97 34.9b ± 24.92 29.0b ± 3.40 30.0b ± 4.26 128.2a ± 27.40 25.1



90

Correlations

The correlation matrix showing the Pearson correlation coefficients (r) and the P-values of the data

(excluding the fatty acid composition) for all the samples are depicted in Table 5.8. Where

applicable, these will be used to illustrate specific points in the discussion.

Table 5.8 Correlation matrix showing the Pearson correlation coefficients (r) and the P-values for

all the samples

Variables 1 2 3 4 5 6 7 8 9 10

1.%Moisture 1 0.0627 -0.7389 0.0506 0.1092 0.1865 0.1059 -0.1378 -0.0182 -0.0922 0 0.0403 <0.0001 0.4998 0.1444 0.0122 0.1569 0.0651 0.0147 0.2184

2.%Ash 0.0627 1 -0.2626 0.3383 -0.2322 -0.1350 -0.2186 0.1199 0.2354 0.0574 0.1030 0 0.0004 <0.0001 0.0017 0.0707 0.0032 0.1089 0.0015 0.4439

3.%Fat -0.7389 -0.2626 1 -0.6490 0.2084 0.1724 0.1481 0.1331 -0.0714 0.1471 <0.0001 0.0004 0 <0.0001 0.0050 0.0206 0.0473 0.0748 0.3407 0.0489

4.%Protein 0.0506 0.3383 -0.6490 1 -0.4835 0.0710 -0.2842 0.0429 0.2907 -0.0263 0.4998 <0.0001 <0.0001 0 <0.0001 0.3433 <0.0001 0.5673 <0.0001 0.7265

5.%pH 0.1092 -0.2322 0.2084 -0.4835 1 -0.1369 0.3060 -0.0328 -0.3550 0.0396 0.1444 0.0017 0.0050 <0.0001 0 0.0093 <0.0001 0.5348 <0.0001 0.4545

6.L* 0.1865 -0.1350 0.1724 0.0710 -0.1369 1 0.0190 0.1541 -0.0131 0.1328 0.0122 0.0707 0.0206 0.3433 0.0093 0 0.7192 0.0034 0.8051 0.0117

7.a* 0.1059 -0.2186 0.1481 -0.2842 0.3060 0.0190 1 0.3286 -0.9334 0.5265 0.1569 0.0032 0.0473 0.0001 <0.0001 0.7192 0 <0.0001 <0.0001 <0.0001

8.b* -0.1378 0.1199 0.1331 0.0429 -0.0328 0.1541 0.3286 1 -0.1322 0.9632 0.0651 0.1089 0.0748 0.5673 0.5348 0.0034 <0.0001 0 0.0120 <0.0001

9.Hue -0.0182 0.2354 -0.0714 0.2907 -0.3550 -0.0131 -0.9334 -0.1322 1 0.9632 0.0147 0.0015 0.3407 <0.0001 <0.0001 0.8051 <0.0001 0.0120 0 <0.0001

10.Chroma -0.0922 0.0574 0.1471 -0.0263 0.0396 0.1328 0.5265 0.9632 0.9632 1 0.2184 0.4439 0.0489 0.7265 0.4545 0.0117 <0.0001 <0.0001 <0.0001 0

The first row of each attribute shows the Pearson correlation coefficient (r) and the second row of each attribute shows the P-value. All the values in bold are significant at a level of P ≤ 0.05.

DISCUSSION

Factors such as production system, genotype, age, stocking density, lighting regime, temperature

and diet have an effect on the overall quality of chicken meat. Therefore the design of this

experiment was such to try and limit the number of factors to production system and genotype.

However, it is well known that genotype and production system effects growth rate and thus the

chickens were slaughtered at different ages but as close as possible to a fixed weight to try and

compensate for these effects. Even so, the Potchefstroom Koekoek still grew slower than the

hybrids or broiler genotype and thus lighter and less fattened chickens were slaughtered (see

Chapter 4). It is argued though that the difference in carcass weight would have a smaller effect

than production system or genotype on the quality attributes.

As emphasised by many authors, it is well known that the chemical composition of the

breast, thigh and drumstick muscles differs. Therefore only the effect of the genotype and

production system would be discussed in more detail. It is also well known that feed has a critical

effect on the chemical composition of chicken meat and in this investigation the same diet was fed

to all the treatments (Chapter 4). The only difference was in the amount of grass/forage found in


91

the free range system. With the exception of the BFR, most of the grass for HFR and all of the

grass for KFR had been consumed within 1 week (Chapter 4). Therefore it is argued that the effect

of feed should be negligible in this investigation.


Post mortem pH decline is one of the most important events in the conversion of muscle to meat,

because of its effect on the meat texture, water holding capacity (WHC), cooking loss, juiciness,

microbial stability and/or shelf-life and colour stability (Fletcher, 1999; Aberle et al., 2001; Honikel,

2004). The rate of pH decline is dependent on the activity of glycolytic enzymes post mortem and

the ultimate pH (pHu) is determined by the initial glycogen reserves of the muscle at mortem

(Lawrie & Ledward, 2006). A low pH is associated with poor meat quality and produces meat with

lower WHC and functionality; a rapid decrease in pH post mortem can also cause similar negative

quality attributes, this phenomenon is also known as PSE meat. A high pHu produces DFD meat

(pH > 6) with poor shelf life, making it a more favourable environment for bacterial spoilage (Aberle

et al., 2001; Honikel, 2004). In chicken meat the pHu value is usually higher, ending at pH≥6.0 at

2-4h post mortem; chicken are known to enter rigor mortis rapidly (Honikel, 2004). The pHu (Table

5.2) values for this study fall within the typical pH region for normal poultry meat (pH≥6). Castellini

et al. (2002) also found pH values in the regions of 5.9 to 6.1 for breast meat and 6.1 to 6.3 for

thigh and drumstick meat. Production system had an effect (P ≤ 0.05) where free range reared

birds either had a lower pHu or a higher pHu than the intensive reared birds. Extensive production

systems are frequently characterized by a lower pHu than intensive reared animals due to lower

stress conditions and less consumption of glycogen reserves immediately prior to slaughter (Enfalt

et al., 1997, Castellini et al., 2002, Fanatico et al., 2007; Wang et al,. 2009). Another possible

reason for the lower pHu in the free range birds are that the increased activity of the birds during

extensive rearing may result in more type IIa muscle fibres which are known to contain a higher

content of glycogen and consequential a higher anaerobic glycolytic potential resulting in a lower

pHu (Lawrie & Ledward, 2006). The higher pHu of the BFR can be ascribed to ante mortem stress.

The free range chickens in this study were collected while they were running about, flapping their

wings and the birds were therefore experiencing a certain amount of ante mortem stress; it was

observed that during the growth phase the BFR were the least active group of birds. During these

stress conditions there is a greater depletion of muscle glycogen ante mortem which will cause a

higher pHu. There was however no effect of production system for the genotype Koekoek and

these results agrees with studies from Ponte et al. (2008), Husak et al. (2008) and Połtowicz &

Doktor (2011) where production system played no significant role in muscle pH. From these

results it could be concluded that some of the chickens may have experienced slight amounts of

ante mortem stress during the capture and carrying and this had an effect on the ultimate muscle

pH, also free range rearing of chickens may also result in lower, more favourable pHu than

intensive rearing.


92

Meat colour is the first meat quality characteristic observed by the consumer and is often

the deciding point whether to purchase the specific product (Fletcher, 2002; Jahan et al., 2005).

Chicken meat is classified as a white meat which is low in redness (a* value) and high in lightness

(L* value) when compared to red meat. The colour of meat is primarily affected by muscle fibre

type, as well as genetics, myoglobin, ante mortem stress and pH (Fletcher, 1999; Fletcher, 2002).

Hue angle defines the colour of the meat and chroma defines colour intensity and

saturation, therefore an increased hue angle will mean less red colour in the meat, while an

increased chroma value will mean a more red colour in the meat. From this study free range

chicken samples presented higher hue and lower chroma values (P ≤ 0.05). Therefore these

results indicate that the free range meat samples showed a less red colour than the intensive

samples. This is also illustrated by the a* value of this study where the free range samples was

lower (P ≤ 0.05) than the intensive samples. The free range birds in this study had a darker (lower

L*) and less yellow (lower b*) (P ≤ 0.05) value than the intensive birds. These results do not agree

with Castellini et al. (2002); Nielsen et al. (2003); Jahan et al. (2004); Fanatico et al. (2005 ; 2007),

Bogosavljević-Bosković et al. (2006) and Husak et al. (2008) where the a* and b* values of outdoor

birds were found to be of a higher value, except in Husak et al (2008) where lower b* values were

found. Fletcher (1999) and Taylor (2004) state that during exercise higher myoglobin red type I

and IIa muscles form, causing the meat to have a more red (higher a* and chroma value and lower

hue angle) and darker (lower L*) colour, therefore it was expected (but not found) that the free

range birds would have a more red and darker colour than the intensive birds. In agreement with

the results in this study, Castellini et al. (2002), Bogosavljević-Bosković et al. (2006) and Husak et

al. (2008) also reported that the outdoor reared birds had less red and darker meat. A reason for

the less red free range chicken meat could be due to the muscle pH, since, colour of meat and pH

are highly correlated (Fletcher, 2002; Lawrie & Ledward, 2006). In Table 5.8 there is a strong

positive correlation between pH and a* value (red colour), as well as negative correlations between

pH and the L* value (lightness) and the Hue angle (less red colour), respectively. These

correlations confirm that pH is partly responsible for the colour of chicken meat. Muscle pHu is

known to influence the myofibrils and consequently the water holding capacity and the colour of the

meat. Lower muscle pH causes shrinkage of the contractile fibres, thereby reducing the WHC and

altering the meat colour by increasing the light scattering (Warris, 2010). Furthermore, a lower pHu

reduces the importance of myoglobin in selectivity by absorbing green light, resulting in meat that

appears less red (Castellini et al., 2002). The HFR birds in this study had a lower pHu than the HI

birds, explaining the less red (lower a*) colour of the meat. The thigh meat of the BFR was

affected by production system as well as all the portions of the KFR with lower a * values, this is

unexpected since the free range samples had either the same pHu value or higher (Table 5.2) than

intensive reared samples and warrants further research. Another reason for the lower red colour

could be due to the defeathering process, where chickens were dumped in hot water to remove the

feathers; this hot water could have affected the colour readings as it was found that it was more


93

difficult to remove the feathers from the hybrid and Koekoek genotype causing these birds to be

left in the water for a longer period. The darker colour (L* value) of the free range birds can be

ascribed to higher myoglobin concentration of the red type I and IIa fibres, due to more exercise.

On the other hand, the lighter colour (L* value) of intensive birds can be ascribed to a higher

percentage fat content in the meat (Table 5.4) due to less activity of these birds. Lipids have high

light reflection properties and cause the meat to appear lighter (Hedrick, 1983). The L* value and

fat were positively correlated (Table 5.8). The lower yellow colour of the free range meat in this

study could be ascribed to less forage/pasture consumption than the mentioned studies where the

free range meat was noted to be more yellow. The high carotenoid pigment content of the grass,

in addition to the composition of the feed mixture, can cause an increase in the yellowness of

chicken meat (Akiba et al., 2001; Toyomizu et al., 2001). All of the outdoor chickens of this study

did have access to a forage area (21 days of age until slaughter) with green grass, but the BFR

chickens did not consume a notisable amount of the grass and the HFR and KFR chickens

consumed all of the grass within the first week (Refer to Figure 4.3 of Chapter 4). Consequently

the grass should not have had an effect on the yellowness of the meat and no differences in the

colour readings were noticed.

Since chickens are monogastric animals the effect of diet is usually reflected in the fatty

acid profile and chemical composition. In this study the chickens were fed the same diet. This

would explain why there were only a few differences found in the chemical composition as well as

the fatty acid profile between genotypes and production system. The fat content of chicken meat

differs between portions with breast meat containing approximately 3% fat, the drumstick between

3.5-5% and the thigh between 7-9%. The breast meat of chicken is generally considered low in fat

(Parkhurst & Mountney, 1988; Mckee, 2003; Fanatico et al., 2007). Similar results were found in

this study (Table 5.4). It is expected that free range reared chicken meat would contain a lower fat

content than intensive reared chicken meat, since higher activity would be likely in these birds. In

this study there was an effect of production system on all the portions of the Koekoek genotype

and the drumstick of the Broiler, where the intensive production system resulted in higher

(P ≤ 0.05) fat content than free range. These results confirm the findings of others where intensive

birds had higher fat contents (Castellini et al., 2002a, 2002b; Castellini et al., 2006 Fanatico et al.,

2007; Bogosavljević-Bosković et al. 2009; Husak et al., 2008). During growth, animal tissue

follows a precise order of maturation of firstly the nervous tissue followed by bone then muscle and

lastly fat (Warris, 2010). Referring back to chapter 4 (Fig. 4.2 and Tables 4.2 and 4.3), KFR

showed better growth and higher body weight than KI. It could be possible that during the growth

of the Koekoek, it favoured fat deposition in the breast and drumstick and lastly in the thigh. Since

KI had a lower growth rate than KFR, and at the time of slaughter the KI did not deposit as much

fat as the KFR in the thigh. Swatland (1994) stated that muscle growth and maturation in chickens

follows a general trend of firstly occurring in the leg muscles, then the breast, and lastly the wing,

but may differ in body proportions between genotypes.


94

Chicken meat is comprised of approximately 60-75% water (moisture); this also differs

between portions (Kauffman, 2001; Keeton & Eddy, 2004). Similar results for moisture content

were found in this study (Table 5.4). According to Pearson & Young (1989), the moisture content

of meat is inversely correlated with the intramuscular fat (IMF) content. In this study a strong

negative correlation (Table 5.8) was observed between IMF content and percentage moisture.

There was also no effect (P>0.05) of production system on the moisture content of the different

meat portions (Table 5.4), except where KFR had higher levels than KI for the drumstick portion.

This was expected since KFR had less (P ≤ 0.05) fat in this portion than KI. The reason for the

moisture content not differing could be ascribed to small or no differences in fat content between

production systems. The same results were found by Bogosavljević-Bosković et al. (2009) where

no difference between production systems was found for moisture content. There was no

correlation (Table 5.8) between pH and moisture content.

Chicken meat is a valuable source of protein; 16-22% (Kauffman, 2001; Keeton, & Eddy,

2004). The protein content of the chicken samples in this study is similar to what is normally found

(Table 5.4). It is known that the protein of meat decreases with an increase fat content (Keeton &

Eddy, 2004), as illustrated further by the strong negative correlation (Table 5.8) between

percentage fat and protein. Consequently it was expected that free range reared birds would

contain more protein, due to their lower fat content, than intensive reared birds. From this study it

is concluded that production system played a role in the protein content of the Koekoek thigh, most

probably due to the lower fat content in the KI’s thigh portion.

Meat contains approximately 1-2% ash, and the ash content of the chicken samples of this

study, lies within this range (Table 5.4) (Keeton & Eddy, 2004; Lawrie & Ledward, 2006). There

was a production system effect for the ash content (P ≤ 0.05) for the Hybrid in the drumstick. A

possible reason for this could be due to selected intake and digestion of small pieces of stones

from the ground which were rich in minerals or due to higher heam pigmentation in the muscle

caused by aerobic exercise of the drumstick (reviewed by Olsson & Pickova 2005). No other

significant effect for ash content were detected and, these results agree with studies from Castellini

et al., (2002a), Fanatico et al., (2005a, b), Kishowar et al., (2005); Bogosavljević-Bosković et al,.

(2006) and Fanatico et al., (2006; 2007). Although there were statistically significant differences

for the effect of production system in the nutritional value of meat, these differences were small

and still fall within the standard nutritional value of chicken and it is questionable if the consumer

would pick up these differences and whether it would have a significant effect on the diet and

health of the consumer.

As previously mentioned; feed plays a very important role in determining the fatty acid

composition of monogastric animals. Free range and intensive chickens were given the same feed

(Table 5.1) which was mainly a maize based diet (~60%) with soybean full fat (~17%) for starter

and grower diets with increased soybean (~36%) for the finisher diet. The main fatty acids present

in chicken meat/fat are palmitic acid (C16:0), palmitoleic acid (C16:1), oleic acid (C18:1), stearic


95

acid (C18:0) and linoleic acid (C18:2) with oleic acid being the highest (Gunstone & Russell, 1954;

Enser, 1999; Lawrie & Ledward, 2006). Similar results were found in this study and together

palmitic acid, palmitoleic acid, oleic acid, stearic acid and linoleic acid comprised ~85% of the total

fatty acids present in all the chicken meat samples (Table 5.5, 5.6 and 5.7). Fatty acid composition

is described by two important ratios PUFA:SFA and n-6:n-3 (Enser et al., 1998). Raes et al. (2004)

suggest that a PUFA:SFA of >0.45 and a n-6:n-3 of <4 contributes to the healthiness of meat

products. In this study there was an overall tendency for the intensive samples to score higher

(P ≤ 0.05) in SFA and MUFA and lower (P ≤ 0.05) in PUFA than the free range samples. There

was also a tendency for free range samples to score higher in the PUFA:SFA ratio. All the

PUFA:SFA ratios in this study were > 0.45, however, all the free range samples have larger ratios

than the intensive samples. Therefore the free range samples would be more favourable and

healthier than the intensive samples as pertaining to the PUFA:SFA ratio. Similar results were also

reported by Castellini et al. (2002), Jahan & Paterson (2007) and Husak et al. (2008).

A few studies have shown that free range chicken meat has a lower n-6:n-3 ratio, making it

a more favourable product than intensive reared chicken meat (Castellini et al., 2002; Jahan &

Paterson, 2007; Husak et al., 2008). It is expected that free range chicken meat products would

contain more n-3 PUFA, since the major food source should be pasture/forage, which is a good

source of α-linolenic acid (C18:3n-3) (Ponte et al., 2008; Jahan & Paterson, 2007). In this study

this was not the case; the n-6:n-3 ratio for all the meat samples was far above the recommended

value (4); some of the free range samples even had higher (P ≤ 0.05) n-6:n-3 ratios, especially the

meat from the thigh and drumstick (Tables 5.5, 5.6 and 5.7), than the intensive samples. This

despite the fact that pasture was available for the birds in the free range system, but as mentioned,

this forage was consumed within the first week of outdoor access and only the KFR and HFR

consumed the forage. The free range chickens thus had a very high n-6 and very low n-3 content.

The linoleic acid (C18:2n6) (Tables 5.5, 5.6 and 5.7) is responsible for the high n-6 content in the

chicken meat. This linoleic acid (C18:2n6c) originates from the maize component in the diet, which

is high in linoleic acid (Storry & Rook 1965). Linoleic acid (C18:2n6) is the essential fatty acid

needed for the synthesis of unsaturated eicosapentaenoic (EPA, 20:5n3) and docosahexaenoic

acid (DHA, 22:6n3) (Enser, 1999). This study also showed low concentrations of EPA and DHA

(Tables, 5.5, 5.6 and 5.7) in the chicken meat, indicating that few EPA and DHA were synthesised

from the linoleic acid. Cook et al. (1993) reports that during stressful times, n-3 stimulates the

body`s physiological processes. Therefore it is speculated that the free range chickens were

exposed to different and more extreme environmental factors compared to the intensive chickens

and thus might have utilized n-3 as an essential nutrient in order to support their immune system

against external stressful stimulations, rather than depositing it in the meat. The same results were

also reported by Jahan et al. (2004) where extensive chicken meat contained lower n-3 fatty acids

and higher contents of total PUFA, n-6 and n-6:n-3 ratios. Givens et al. (2011) also reported lower

n-3 fatty acids, EPA and higher n-6:n-3 ratios in free range birds. It is also important to remember


96

that free range birds are usually given different diets than the normal conventional chickens, which

are more suitable for free range rearing and might affect the fatty acid profile in different ways. For

this study`s purposes the feed given to the intensive and free range birds were of the same

composition, to eliminate the effect of feed and to investigate only the effect of genotype and

production system.

In this study there was also a trend for BI to contain higher (P ≤ 0.05) oleic acid (C18:1n9c)

and lower (P ≤ 0.05) Linoleic acid (C18:2n6) than the BFR and all the other samples. This also

caused the BI to contain higher (P ≤ 0.05) MUFA and lower (P ≤ 0.05) PUFA, as well as a lower n-

6 content thereby lowering the n-6:n-3 ratio. As mentioned, the feed given to the chickens was

mainly a maize based diet (~60%), and also contained lower levels of soybean (~17% and ~36%),

which is high in oleic acid. Therefore the fatty acid content of the BI meat would have reflected this

trend since the chickens were all fed the same diet and the diets` fatty acids are directly

incorporated into the meat of monogastric animals (Tat et al., 2007; Fébel et al., 2008). This

phenomenon was unexpected and would warrant further research.

Effect of genotype

The effect of genotype on the physical attributes and chemical composition was less substantial in

comparison to that of production system. There was no effect of genotype (P>0.05) detected in

the muscle pH (Table 5.4) nor in the fatty acid composition (Tables 5.5, 5.6 and 5.7). However, it

would seem that genotype had a slight effect on the colour, where Hybrid and Koekoek had a more

green (lower a*), more blue (lower b*), and lower chroma than Broiler for all the portions, Hybrid

also had higher hue values than Koekoek and Broiler genotypes. Koekoek genotype had a slightly

darker (lower L*) value than genotypes Broiler and Hybrid for portions thigh and drumstick (Table

5.5). The significant darker colour of the thigh and drumstick of the Koekoek could be related to

ante mortem stress causing greater depletion of muscle glycogen, which causes a higher pHu.

However, the pH values (Table 5.4) did not differ (P ≤ 0.05) in these two portions. Alternatively,

the proportion of dark (red) and light (white) fibres types could also influence the colour – the

Koekoek genotype is renowned for its ability to walk and maintain a high level of activity as it is

actually a village chicken; this continuous activity would result in more dark (red) muscle fibres in

the leg muscles. However, a less red (greener) colour was detected in the meat samples. A

similar red colour (higher a* value) was expected in the Hybrid and Koekoek genotypes (slower

growing birds than broiler) due to higher myoglobin concentration in muscles of older birds (Miller,

1994; Husak et al., 2008). Another possible reason of the difference in colour could be linked to

the actual measurement of the colour. Bianchi and Fletcher (2002) and Sandusky and Heath

(1996) found that meat sample thickness, position of the colour instrument on the meat as well as

background colour can also radically affect instrumental colour readings. Although not quantified,

Koekoek meat samples were overall thinner than the Boiler and Hybrid meat samples, which could

have affected the instrumental colour. It is also important to keep in mind that these chickens were


97

dumped in hot water to remove feathers; this may have influenced the colour readings. Especially

the Koekoek and Hybrid genotypes, where the temperature and time in the scalding water may

have differed from broiler since their feathers did not remove as easily as the latter. Although there

were differences in the colour readings between genotypes, these differences were so slight that it

is doubtful that any consumer would have seen these differences with the naked eye.

It is clear that there was a genotype effect in the moisture content of the different portions.

Broiler had higher (P ≤ 0.05) moisture content than Koekoek in the breast portion, while the

opposite was true in the thigh portion. Fanatico et al. (2005) established that slow growing birds

had higher percentage moisture content than fast growing birds. The reason for the Koekoek to

have a lower moisture content than the Broiler is due to the higher (P ≤ 0.05) fat (Table 5.4)

content in the breast; fat and moisture contents are negatively correlated to each other (Table 5.8).

The differences in the fat content between species and muscles are often a result of the

differences in the muscle fibre types. Slower growing birds (in this case the Koekoek) are older in

age than the Broiler when they attain the targeted slaughter weight and therefore had more time to

deposit fat in the breast muscle, also more red type IIa fibres could have formed in the breast meat

of the Koekoek due to more frequent flapping op the wings (Swatland, 2000; Lawrie & Ledward,

2006). Although this behaviour was not quantified, it was observed and warrants further research.

It is generally known that the red fibre muscles have a higher concentration of triglycerides and

phospholipids than white muscles (Taylor, 2004; Wood et al., 2003). However, the same trend

was not observed in the Koekoek thigh meat, this could be due to the age of the bird and

exercising of the muscle. As the Koekoek is late maturing, the birds were slaughtered before their

growth inflection point (the age at which gain is at its maximum) at the stage where muscle

development was favoured, due to the higher exercise level, before fat deposition occurred in the

thigh (Gordon & Charles, 2002). Therefore it can be concluded that slower growing genotypes had

higher moisture and lower fat content in the thigh, and faster growing genotypes score lower fat

and higher moisture in the breast meat. Results by Fanatico et al. (2007) and Husak et al. (2008)

confirmed that slower growing birds contained higher protein content, since they are late maturing

and this increase is accompanied by a reduction in fat content.

CONCLUSIONS

The aim of this study was to perform an explorative study to determine the nutritional composition

and physical attributes of the Broiler, Hybrid hybrid and Potchefstroom Koekoek reared in intensive

and free range production systems.

The results of this study indicate that the effect of production system has a much larger

influence on the physical and chemical composition of the meat than does genotype. Free range

(outdoor access) resulted in lower muscle pH, darker (L* value), less red (a* value) and less yellow

(b* value) chicken meat. It also influenced the chemical composition in different carcass portions;


98

for example, a lower fat content in the thigh and higher protein in the breast of the Broiler. The

Hybrid hybrid`s chemical composition were not strongly influenced by the effect of production

system. Rearing chickens in a free range environment increased the PUFA:SFA ratio, making it

beneficial to human health. Genotype resulted in little difference other than affecting the lightness

(L* value) of the Koekoek and the a*, b* and hue values of the Hybrid hybrid, as well as the

moisture, fat and protein content of the Broiler and moisture and fat content of the Koekoek. It

would seem that Hybrid could possibly be a more suitable alternative for free range rearing than

the Broiler genotype.

This study has shown that although there were significant differences between production

systems and genotype, the differences were small, and thus the question arises whether a

consumer would discern these differences when they consume the meat?

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(edited by W.K., Jensen, C., Devine & M. Dikeman) Pp. 876-882. New York. Elsevier

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muscle of broiler chickens. British Poultry Science, 42, 197-202.


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651-667.


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CHAPTER 6

EFFECT OF REARING SYSTEM AND GENOTYPE ON THE SENSORY, PHYSICAL AND CHEMICAL QUALITY OF CHICKEN MEAT

ABSTRACT

Modern consumers are more health conscious and are shifting to more naturally produced

products such as free range chicken. Commercial broilers strains are not suitable for free range

rearing under local conditions and an alternative genotype is required, which will suite the South

African market with the same meat quality as a broiler. The main objective of this study was to

investigate the impact of genotype and production system on the sensory and chemical, including

fatty acid, and instrumental meat quality characteristics of cooked chicken breasts (pectolaris major

muscle). Three chicken genotypes, Broiler (fast growing bird), Hybrid (medium growing bird) and

Potchefstroom Koekoek (slow growing bird) were reared in two production systems (intensive and

free range) and fed the same formulated feed, ad libitum, and slaughtered at the age of 42, 56 and

91 days, respectively. Overall, the results of this study indicate that the differences were mainly

genotype driven and not influenced by production system. Hybrid scored higher (P ≤ 0.05) in

chicken flavour and aroma than the Broiler and Koekoek. The Hybrid also had a higher

percentage drip loss (P ≤ 0.05) than Broiler and Koekoek. Broiler had a higher (P ≤ 0.05) shear

force value than Koekoek. With regard to production system, Broiler free range had a higher

(P ≤ 0.05) pH than Broiler intensive and higher (P ≤ 0.05) n-6:n-3 ratios were found in the free

range samples. Hybrid free range also had a higher (P ≤ 0.05) fat content than Hybrid intensive.

Although there were significant differences (P ≤ 0.05) in sensory, chemical and physical attributes,

the differences were so small that it could be argued that if these treatments were to be presented

to the consumer, the latter would not notice any difference. None the less, it seems as if the

Hybrid is the more suitable genotype for free range rearing in terms of aroma and flavour.

Keywords: Broiler, Potchefstroom koekoek, Hybrid hybrid, Meat quality, Production system,

Genotype


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INTRODUCTION

The modern consumer generally tends to be more aware of the health and nutritional value of the

food consumed, is more animal welfare conscious, desires more naturally produced products and

supports a more sustainable way of farming (Sundrum, 2001). Needless to say, together with

these requirements, the consumer still expects a high standard regarding the taste of the food

(Hoffman & Cawthorn, 2012). Similarly, as pertaining to the meat market, the interest of the

consumer has grown towards quality aspects, rather than just quantity; this mind shift of the

consumer has provided opportunities for market segmentation of speciality products, such as free

range and organic. Although consumers expect a higher degree of welfare in free range chickens,

this is only true if slow-growing chicken strains are used (Castellini et al., 2008). Furthermore,

consumers believe that the meat of free range chickens are healthier and tastier than birds reared

in confinement and their overall perception is positive towards free range production systems

(Fanatico et al., 2007; Branciari et al., 2009).

In South Africa, the normal fast growing commercial broiler is currently used for both free

range and intensive production. These chickens reach market weight as early as 28-32. As a

result of the genetic selection, for fast growing animals, their behaviour has changed to reduced

kinetic activity (Schütz & Jensen, 2001; Branciari et al., 2009). Therefore, broilers have a habit of

staying indoors, being dormant and less active (Smith & Carpernter, 1970; Lewis et al., 2005).

This rapid growth has also led to concerns about animal welfare, since more leg disorders and a

higher mortality rate occur. The latter, combined with the slower growth in extensive sytems (i.e.

older birds) resulting in higher costs for feed and less production cycles could result in higher

production costs for the farmer. Also, Dransfield and Sosnicki (1999) reported that selection for

fast growth and high yield may have a negative effect on the sensory and functional qualities of the

meat; therefore it is possible that differences in meat quality may exist between fast and slow

growing birds (Lonergan et al., 2003).

The French Label Rouge, which requires outdoor access and a slow growing chicken

genotype, has been very successful in the European sector, despite a higher retail price than

intensive poultry products (Westgren, 1999). This high quality meat is more appropriate for a

speciality gourmet market (Fanatico et al., 2006). Farmers in South Africa utilize the same fast

growing chicken lines, which has been bred specifically for intensive rearing for their extensive

rearing methods. However, the suitability of these fast-growing broilers, for outdoor production and

specialty markets, has not been extensively researched (Fanatico et al., 2005). A few studies have

evaluated the sensory quality of meat from fast, medium and slow growing birds, although the

large variation in the production systems and type of birds (genotype, strain and age) used might

skew the results (Touraille et al., 1981; Castellini et al., 2002b; Lonergan et al., 2003; Fanatico et

al., 2006; Fanatico et al., 2007). Such studies have never been done in a South African

environment or on indigenous crossbred (with commercial broilers) chickens.


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Castellini et al. (2008) reported that only slow-growing chicken strains can completely

benefit from an extensive rearing system and that the fast growing strains are considered slow to

adapt to change. Therefore, a slower growing chicken line is needed, that can adapt to the harsh

conditions of the South African weather, can eat the forage in an extensive production system and

still give the same meat quality as the broiler.

Tenderness, juiciness and flavour are the three important meat quality characteristics that

determine consumer preference. It is important to evaluate the effects of genotype and production

system on the sensory attributes and consumer preferences in order to assist producers in making

informed choices regarding suitable production systems. The aim of this study was to investigate

the effect of chicken genotype (Broiler, Ross x Potchefstroom Koekoek hybrid and Potchefstroom

Koekoek) and production system (intensive or free range) on various meat sensory quality

characteristics (flavour, aroma, initial juiciness, sustained juiciness, first bite and residue), physical

measurements (pH, drip loss, cooking loss, WHC and Warner Bratzler instrumental tenderness)

and chemical analysis (proximate and fatty acid composition) of chicken meat. This study

excluded the quantification of the effect of gender (male or female) on the sensory quality

characteristics and quality of the meat.



Refer to Chapter 3 for materials and methods on experimental bids, location, handling and

slaughtering procedure of the different chicken treatments.

Experimental units

At the meat science laboratory each carcass was skinned, the breast muscles removed by cutting

from the clavicale furcula bone alongside the keel bone, the weight recorded and the meat

vacuum-packed and frozen at -18°C until further analysis. The experimental units included six

meat treatments which consisted of either a Broiler, a Hybrid or a Koekoek sample, each reared

intensively or free range. The following acronyms are used to describe the six different treatments:




Each experimental unit consisted of six replications (n = 6). The sensory analysis and physical

measurements were performed on the cooked right breast, except for the pH which was measured


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on the raw right breast, of the carcass while the proximate analyses were performed on the cooked

left breast muscle of the carcass. Therefore, the analyses were performed on 36 birds.

Descriptive sensory analysis

Prior to conducting the sensory analyses, the breasts were removed from the freezer, maintained

in their vacuum-packed bags, and defrosted for a 6 h period in a cold room (4°C). The sensory

analysis consisted of six meat treatments with six consecutive replications of the sensory test, thus

the experimental design is equal to 36 (6 treatments x 6 replications) treatment combinations.

Before each of the sensory analysis sessions, the left and right breast muscles of the chicken were

placed inside separately marked roasting oven bags (GLAD™, South Africa). The roasting bag

with the meat samples was then placed on a stainless steel grid fitted onto an oven roasting pan.

Thermocouple probes attached to a handheld digital temperature monitor (Hanna Instruments

South Africa) were placed inside the centre of each of the meat samples, where after, the roasting

bags were closed by the use of a metal tie (AMSA, 1995). The prepared samples were then

placed inside two conventional ovens (Defy, Model 835) connected to a computerised monitoring

system responsible for the regulation of the temperature (Viljoen et al., 2001). The ovens were

pre-heated to 160°C (AMSA, 1995). The meat samples were removed from the oven when an

internal temperature of 75°C was attained (AMSA, 1995). After removal from the roasting bags the

samples were allowed to equilibrate to ambient temperature (± 15 min) where after the right

breasts were cut into 1 x 1 x 1 cm cubes, individually wrapped in aluminium foil squares and

placed into glass ramekins with a randomized three digit code. Before the samples were served to

the panellists for evaluation, the ramekins containing the meat samples were placed in a preheated

oven (100°C) and reheated for 10 minutes where after they were immediately served to the panel.

Descriptive sensory analysis was performed on the six meat treatments. A panel of eight

judges were selected based upon previous experience with the sensory analysis of meat. The

panellists were trained according to the guidelines for sensory analysis of meat by the American

Meat Science Association (AMSA, 1995) and the generic descriptive sensory analysis technique

as described by Lawless and Heymann (2010). The panel undertook four training sessions and

during each session the panellists received 1 x 1 x 1 cm cubes of meat from the six meat

treatments using extra bird breasts from the same sample population. The panel decided on six

sensory attributes: chicken aroma and flavour, as well as initial and sustained juiciness, tenderness

(first bite) and residue. The definitions for each of the attributes are described in Table 6.1. The

sensory attributes were analysed using an unstructured line scale with zero (low intensity) on the

left hand side and 100 (high intensity) on the right hand side (AMSA, 1995).

The test re-test method was used for the sensory analysis and the six treatments were

replicated six times. The panellists received the six meat treatments in a complete randomised

order, while seated in individual tasting booths fitted with Compusense five® (Compusense,

Guelph, Canada). The samples were analysed by completing the questionnaire assembled during


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the training sessions. The sensory analysis sessions took place inside a temperature-controlled

(21°C) and light-controlled (artificial daylight) room (AMSA, 1995). In order to cleanse and refresh

their palates between evaluations the panellists received distilled water (21°C), half an apple and

water biscuits (Carr, UK).

Table 6.1 Definition and scale of each attribute used for the descriptive sensory analysis of the

chicken breasts

Sensory attribute Description Scale

Chicken Aroma Aroma associated with chicken experienced as soon as the aluminium foil is removed


Chicken Flavour Flavour associated with chicken prior to swallowing 0 = Extremely bland 100 = Extremely intense

Initial Juiciness The amount of fluid exuded from the cut surface when pressed between the thumb and forefinger


Sustained Juiciness The level of juiciness perceived after the first 5 chews using the molar teeth 0 = Extremely bland 100 = Extremely intense

First Bite The impression of tenderness perceived after the first 5 chews using the molar teeth


Residue The amount of residue left inside the mouth after the first 10 chews 0 = None 100 = Abundant

Physical measurements

pH

The pH of the six meat treatments, of each replication, was measured after thawing for 6 h. This

measurement was done immediately after the meat was removed from the packaging and before

the start of the cooking process. The pH was measured by means of a Crison pH 25 handheld

portable pH meter (Lasec (Pty) Ltd, South Africa) that had been calibrated before each set of

readings with the standard buffers (pH 4.0 and pH 7.0) provided by the manufacturer.

Drip loss

When the breast muscle was removed from the carcass, the weight (g) was documented before

being vacuum-packed and frozen (-18°C) for approximately eight weeks. After the breast meat

was defrosted in a fridge (4°C) for 6 h it was removed from the packaging and blotted dry with

tissue paper and weighed again (g). The difference in the weight of each of the samples was

calculated as the percentage drip (thaw) loss.

Cooking loss

The total weight loss during cooking (cooking loss) of the six treatments for the six replications was

determined by using the method described by AMSA (1995). The breast muscle from each

treatment was weighed (g) and documented before the cooking. After the cooking process, the


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meat was removed from the cooking bag and allowed to cool down to ambient temperature,

approximately 10-15 min. Before recording the final weight (g), the meat was blotted with tissue

paper to remove excess moisture. The difference in the weight of each of the samples was

calculated as the percentage cooking loss.


The water holding capacity test was performed according to Trout (1988). A cooked meat sample

from each of the six treatments and six replications was used. The meat samples was cut into

small pieces and 0.50 g thereof was placed on top of a filter paper (Lased, Paper Filter, grade 292,

diameter 90 mm, part nr. FLAS3205090). The filter paper together with the meat sample was

placed between two Perspex plates and a standard pressure of 588 N was enforced on the plates

for 60 sec. A photograph was then taken of the filter paper showing the expelled liquid and meat

areas. Image J Software (Version, 1.36b, NIH Image) were used to calculate the ratio between the

liquid (outer) and meat (inner) purge area to indicate the water holding capacity of the meat

sample.

Warner Bratzler Shear Force

The instrumental tenderness of the cooked meat samples was analysed by using the Warner

Bratzler shear force (WBSF) test as described by Honikel (1998). Each of the six treatments (six

replications) was used for the WBSF test. From the centre of the cooked meat sample, two

adjacent 1 x 1 cm meat strips were cut parallel to the muscle fibre direction. Each of the meat

strips were wrapped in aluminium foil and placed in the refrigerator (4°C) for 24 h. The meat strips

were cut to produce a total of five rectangular cubes each with a length of two centimetres. An

Instron Universal Testing Machine (Model 2519-107, Advanced Laboratory Solutions) fitted with a

Warner-Bratzler (WB) blade was used to determine the force (Newton) necessary to shear a

cooked rectangular meat cube perpendicular to the muscle fibre direction. The WB fitting was a 1

mm thick triangular (V-notch) blade with a semi-circular cutting edge (radius of 0.508 mm). The

Instron Universal Testing Machine operated with a 2 kN compression load at a compression speed

of 200 mm/min. The shear force value of each of the samples was recorded in Newton (N) and a

higher value is indicative of a tougher sample.

Chemical analysis

Sample preparation

The cooked left breast muscle (sample) from each of the treatments were homogenised, vacuum

sealed and placed in a -18°C freezer for one week until the chemical analysis were performed.

The samples were thawed at 4°C for 6 h before each of the analysis. All of the analysis was

performed in duplicate.


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Proximate analysis

The proximate chemical analysis (%) consisted of total moisture, protein, lipid and ash content of

the 36 chicken breast muscles. The moisture content (%)(100°C, 24 h) was analysed by drying a

2.5 g homogenized meat sample according to the Association of Official Analytical Chemist`s

Standard Techniques (AOAC) method 934.01 (AOAC, 2002a). The ash content (%) (500°C, 6 h)

of the moisture free sample was determined by the official AOAC method 942.05 (AOAC, 2002b).

The total lipid (%) (intramuscular fat) content of a 5 g homogenised cooked meat sample was

determined by using the chloroform:methanol (1:2 v/v) extraction method of Lee et al. (1996). To

determine the total crude protein content (%), a 0.15 g defatted, dried and finely grounded meat

sample was analysed using a Leco Nitrogen/Protein Analyser (FP- 528, Leco Corporation). The

Leco was calibrated with EDTA calibration samples (Leco corporation, 3000 Lakeview Avenue, St.

Joseph, MI 49085-2396, USA, Part no. 502-092, Lot no. 1055) before each of the analysis

sessions. The Dumas combustion method 992.15 (AOAC, 2002c) was used and the results were

expressed in % nitrogen (N). The nitrogen (%) was multiplied with the conversion factor of 6.25 to

determine the crude protein (%) present in the meat sample.

Fatty acid analysis

The fatty acid profile of the six meat treatments of each replication was determined by using the

fatty acid methyl esters (FAME) extraction method as described by Folch et al. (1957). A 2 g

sample was extracted by the use of a chloroform:methanol (2:1 v/v) solution. The extraction

solvent contained 0.01% butylated hydroxytoluene (BHT) as an antioxidant. A polytron mixer

(WiggenHauser Homogenizer, D-500 fitted with a standard shaft 1; speed setting D) was used to

homogenise the meat sample with the extraction solvent. Heptadecanoic acid (C17:0) was used

as an internal standard (catalogue number H3500, Sigma-Aldrich Inc., 3050 Spruce Street, St.

Louis, MO 63103, USA) to quantify the individual fatty acids present within the meat sample. A

250 µL sub-sample of the extracted lipids was transmethylated for 2h at 70°C and a

methanol/sulphuric acid (19:1; v/v) solution (2 ml) was used as the transmethylating agent. After

the mixture was cooled to room temperature, FAME with water and hexane followed. The top

hexane phase was transferred to a spotting tube and dried under nitrogen. After drying 50 µL of

Hexane were added to the FAME sample, and 1 µL of the sample was injected into the gas-

chromograph (Termo-Electron S.p.A, Rodana, Milan, Italy) equipped with a 60 m BPX70 capillary

column with an internal diameter of 0.25 mm and 0.25 µm film (SGE International, Ringwood,

Victoria, Australia) and flame ionized detector. The gas flow rate of the carrier, hydrogen, was 30

mL/min. The temperature settings were as follows: initial temperature 60°C, injector 220°C,

detector 260°C and the final temperature at 160°C. The injection volume was 1 µL with a run time

of approximately 45 min. The FAME of the meat samples was compared to a standard FAME

mixture (Supelco™ 37 Component FAME mix C4-C24, CAT, no. 47885-U. Supelco, North Harrison


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Rd, Bellefonte, PA 16823-0048, USA) to identify the values. The results were recorded as

percentage (%) of the total fatty acids.

Statistical analysis

Experimentally the study consisted of a randomised factorial block design with six treatments (3

Chicken lines x 2 rearing methods) and six replications. The trained panel consisted of eight

judges and the six treatments were evaluated for the six sensory attributes established during the

training sessions. The model for the experimental design is indicated by the following equation:

Yij = µ + βj + bi + gk +(bg)ik + εijk

The terms within the model are defined as; the overall mean (µ), the effect of the block (βj), the

effect of chicken genotype (bi) the effect of rearing method (gk), the effect of the interaction

between chicken genotype and rearing method (bg)ik and εijk is the error associated with the effect

of the block, chicken genotype, rearing method and interaction of the former and the latter. The

sensory, physical and proximate data were subjected to an analysis of variance (ANOVA). The

Shapiro-Wilk test was performed to test for normality (Shapiro & Wilk, 1965). All of the outliers

were identified and removed before final analysis of the ANOVA`s. The Least Significant

Differences (LSD) was calculated at a 5% significance level to compare the treatment means.

Results were defined as being not significant at P > 0.05 and significant at P ≤ 0.05. Correlations

were made between the sensory attributes, physical characteristics and proximate composition by

means of the Pearson`s correlation coefficient (Snedecor & Cochran, 1980). Principal Component

Analysis (PCA) and Discriminant Analysis (DA) were performed to illustrate the relationships

between the sensory, physical and proximate data (Rencher, 2002). SAS™ statistical software

(Statistical Analysis System, Version, 9.2, 2006, SAS Institute Inc., CARY, NC, USA) was used for

the ANOVA) while the multivariate statistical analysis was performed using XL STAT™ statistical

software (Version 2011, Addinsoft, New York, USA).

RESULTS

Sensory attributes

The sensory means with standard deviations (± SD) of the six different treatments (t-tests) as

affected by genotype and production system are presented in Table 6.2. Genotype within

production system played a role (P ≤ 0.05) on the attributes: chicken flavour, chicken aroma and

residue. The HI sample scored the highest chicken flavour which differed (P ≤ 0.05) from the BI

and KI samples, which did not differ from each other. The HFR had a significantly (P ≤ 0.05) higher

chicken flavour than KFR. When considering the attribute chicken aroma, RKI scored higher


111

(P ≤ 0.05) than BI whilst the KI had the lowest score. With regard to residue, BI was significantly

different (P ≤ 0.05) from HI and KI, although KI and HI did not differ from each other. HFR had a

lower (P ≤ 0.05) residue score than BFR and KFR.

There were no differences between any of the genotypes or production systems as

pertaining to initial juiciness. Although some of the treatments differed statistically when

considering sustained juiciness and tenderness, they were still of similar magnitude, indicating that

the samples were perceived to be very similar.

Table 6.2 The mean scores (± SD) for the sensory attributes of chicken breast as affected by

genotype and production system

Attributes Broiler Hybrid Koekoek


Chicken flavour 54.2bc ± 10.44 56.0abc ± 9.04 58.0a ± 9.88 56.0ab ± 8.98 54.5bc ± 10.42 52.9c ± 10.48 3.62

Chicken aroma 51.9bc ± 5.35 53.4b ± 5.43 55.9a ± 5.63 53.4ab ± 6.29 51.0c ± 7.63 52.4bc ± 7.13 2.13

Initial juiciness 49.0 ± 9.30 51.0 ± 11.02 50.2 ± 8.05 49.9 ± 9.61 50.4 ± 9.20 49.1 ± 8.92 3.00

Sustained juiciness 47.6b ± 10.68 50.4ab ± 10.84 50.6ab ± 10.05 52.4a ± 6.86 51.7ab ± 9.55 49.8ab ± 10.50 4.04

Tenderness 64.9 ± 14.73 63.7 ± 10.43 64.0 ± 11.05 65.0 ± 10.08 62.0 ± 11.45 60.6 ± 14.23 4.04

Residue 14.1a ± 5.48 12.3ab ± 5.12 12.0bc ± 5.07 10.4c ± 5.47 12.5b ± 6.51 12.3ab ± 5.48 1.83

Standard Deviation (SD); LSD Least Significant Difference (LSD) abMeans in rows with different superscripts are significantly different at P ≤ 0.05

* Means determined by an unstructured line scale (0 = low intensity, 100 = high intensity)

Physical attributes

The physical attributes measured included: pH, percentage drip loss, percentage cooking loss,

water holding capacity and instrumental shear force of the meat samples. The t-tests with means

and standard deviations (± SD) for the instrumental analysis of the different treatments as affected

by genotype and production system are presented in Table 6.3. According to Table 6.3, the effect

of production system only differed (P ≤ 0.05) in the physical attribute pH within the broiler

genotype; BFR measured significantly lower (P ≤ 0.05) than BI.

With regard to the effect of genotype within production system, the attributes: % drip loss,

% cooking loss, WHC and shearforce were affected. The HFR had significantly higher (P ≤ 0.05) %

drip loss than BFR and KFR. For % cooking loss and shear force, BI had higher values in both

these attributes and differed significantly (P ≤ 0.05) from KI. The KI had the highest WHC which

differed (P ≤ 0.05) from HI, although both these treatments did not differ (P > 0.05) from BI.


112

Table 6.3 The mean scores (± SD) for the physical characteristics of cooked chicken breast as




pH 5.8b ± 0.07 6.0a ± 0.11 6.0a ± 0.11 6.0a ± 0.07 5.9ab ± 0.05 5.9ab ± 0.07 0.10

% Drip loss 13.4ab ± 5.76 9.7bc ± 3.48 11.1ab ± 6.18 16.1a ± 10.51 6.8bc ± 2.46 6.2c ± 2.42 6.23

% Cooking loss 23.4a ± 5.77 25.9a ± 9.28 20.9ab ± 2.22 19.5ab ± 7.07 16.2b ± 1.29 21.4ab ± 5.56 6.95

WHC 3.3ab ± 0.47 3.4ab ± 0.37 3.1b ± 0.28 3.3ab ± 0.31 3.5a ± 0.12 3.1ab ± 0.31 0.40

Shear force (N) 24.0a ± 5.54 25.6a ± 7.32 20.3ab ± 3.29 20.9ab ± 4.40 17.9b ± 3.65 22.3ab ± 4.07 5.93

Standard Deviation (SD) ; Water holding capacity (WHC); Least Significant Difference (LSD) abMeans in rows with different superscripts are significantly different at P ≤ 0.05

Proximate composition

The proximate analysis results of the cooked breast meat samples as affected by genotype and

production system are indicated in Table 6.4. Neither genotype nor production system had any

effect on the moisture and protein content of the cooked chicken breast muscle. With regard to the

influence of production system within a genotype, there were no differences (P > 0.05) for any of

the proximate components, except for intramuscular fat (%) content (P ≤ 0.05) between HI (3.0

g/100g) and HFR (3.6 g/100 g).

Regarding the effect of genotype on the proximate components, only intramuscular fat (%)

content and ash differed. The BI (3.9 g/100 g) with the higher intramuscular fat (%) content,

differed (P ≤ 0.05) from KI (3.1 g/100 g) and HI (3.0 g/100 g) although the latter two genotypes did

not differ (P>0.05) from each other (Table 6.4). BI, with the higher ash content, differed (P ≤ 0.05)

from KI, although neither of these two treatments differed from HI, which contained the highest ash

content.

Table 6.4 The mean scores (± SD) for the proximate composition of cooked chicken breast as




Moisture 64.7 ± 1.42 65.3 ± 0.78 65.4 ± 1.25 65.3 ± 1.86 65.3 ± 1.38 63.9 ± 1.69 1.76

Protein 30.7 ± 1.14 30.3 ± 0.64 31.4 ± 1.90 30.9 ±1.98 31.5 ± 0.75 32.8 ± 1.33 1.53

Fat 3.9a ± 0.65 3.9a ± 0.49 3.0c ± 0.36 3.6ab ± 0.47 3.1bc ± 0.46 3.2bc ± 0.36 0.56

Ash 1.3a ± 0.09 1.4ab ± 0.11 1.4ab ± 0.11 1.4ab ± 0.16 1.2b ± 0.09 1.3b ± 0.09 0.14



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Fatty acid composition

The mean percentages and standard deviations (± SD) for the fatty acid composition of the cooked

meat of the six different treatments are presented in Table 6.5. All of the fatty acids present in the

treatments were analysed and are presented in the table although only specific fatty acids will be

discussed. In general the fatty acid composition of the different treatments did not differ

significantly.

The concentration of polyunsaturated fatty acid (PUFA) was the highest, followed by

saturated fatty acid (SFA) and then monounsaturated fatty acid (MUFA) in all the chicken samples.

When considering the overall SFA content, there were no significant difference between the

different chicken samples (P > 0.05). As pertaining to production system, there was a difference

(P ≤ 0.05) between KI and KFR for Stearic acid (C18:0). There were also differences (P ≤ 0.05)

between production systems within a genotype for the fatty acids Arachidic acid (C20:0) and

Behenic acid (C22:0) between Hybrid and Broiler respectively, although there were significant

differences, these are very small. There were minor, less than 1.0%, but significant differences

(P ≤ 0.05) for genotype within a production system for the individual SFAs Myristic acid (C14:0),

Arachidic acid (C20:0), Heneicosanoic acid (C21:0) and Behenic acid (C22:0).

The effect of genotype within a production system on the overall MUFA content indicated

that HI and KI differed significantly (P ≤ 0.05) from BI. Oleic acid (C18:1n9c) was the major MUFA

found with the highest concentration in all the chicken treatments with differences (P ≤ 0.05)

between genotypes within a production system. The BI with the highest percentage differed

(P ≤ 0.05) from HI and BFR differed (P ≤ 0.05) from KFR. Although there were differences

(P ≤ 0.05) for the effect of genotype within a production system for the fatty acids Elaidic acid

(C18:1n9t), Eicosenoic acid (C20:1n9) and Erucic acid (C22:1n9), the difference were very minor

(< 0.1%). There were also differences (P ≤ 0.05) between production system within a genotype for

the individual MUFA Eicosenoic acid (C20:1n9) and Erucic acid (C22:1n9), but these were also

very minor (< 0.1% difference).

Regarding the total PUFA content; genotype and production system had an effect

(P ≤ 0.05). HFR, with a higher PUFA content differed (P ≤ 0.05) from BFR whilst HFR also differed

(P ≤ 0.05) from HI (Table 6.5). For the individual PUFA`s for production system within a genotype,

Linoleic acid (C18:2n6c) differed (P ≤ 0.05) between HFR, with the higher concentration, and HI.

Other individual fatty acids that differed (P ≤ 0.05) for production system within a genotype were L-

Linolenic acid (C18:3n6), α-Linolenic acid (C18:3n3); Docosadienoic acid (C22:2),

Eicosapentaenoic acid (EPA; C22:5n3) and Docosahexaenoic acid (DHA; C22:6n3), but again the

differences were small (<1.0%). There were also small (<1.0%), but significant (P ≤ 0.05)

differences for the individual fatty acids L-Linolenic acid (C18:3n6), α-Linolenic acid (C18:3n3),

Eicosatrienoic acid (C20:3n6), Docosadienoic acid (C22:2), C22:5n3 (Docosapentaenoic acid) and

DHA (C22:6n3) for the effect of genotype within a production system.


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The polyunsaturated to saturated fatty acid ratio (PUFA:SFA) did not differ (P > 0.05) for

any of the treatments. The omega 3 to omega 6 ratio (n-6:n-3) did however differ (P ≤ 0.05) for the

effect of production system. For the effect of production system within a genotype, BFR had a

higher P ≤ 0.05) n-6:n-3 ratio than BI. HFR also had a higher (P ≤ 0.05) ratio than HI.


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Table 6.5 The mean scores (± SD) for the fatty acid composition (% of total fatty acids) of cooked

chicken breast as affected by genotype and production system



SFA C14:0 0.4ab ± 0.12 0.4ab ± 0.10 0.5ab ± 0.20 0.5a ± 0.13 0.5ab ± 0.25 0.3b ± 0.21 0.21

C15:0 0.1 ± 0.2 0.1 ± 0.03 0.13 ± 0.04 0.1 ± 0.02 0.1 ± 0.03 0.1 ± 0.03 0.04

C16:0 22.0 ± 2.85 21.9 ± 5.53 25.7 ± 7.63 19.0 ± 4.91 24.0 ± 6.33 18.7 ± 10.0 7.77

C18:0 9.8b ± 1.22 10.3ab ± 0.5 10.3ab ± 1.16 10.2ab ± 1.00 9.5b ± 1.04 11.3a ± 1.47 1.31

C20:0 0.3ab ± 0.03 0.4a ± 0.09 0.3b ± 0.08 0.4a ± 0.12 0.3b ± 0.07 0.2b ± 0.07 0.09

C21:0 0.1b± 0.01 0.1a ± 0.01 0.1b ± 0.01 0.1b ± 0.01 0.1b ± 0.01 0.1b ± 0.01 0.01

C22:0 1.2a ± 0.23 1.1ab ± 0.25 1.13ab ± 0.18 0.9bc ± 0.22 0.9c ± 0.19 0.7c ± 0.23 0.27

C24:0 0.1 ± 0.02 0.1 ± 0.02 0.1 ± 0.01 0.1 ± 0.02 0.1 ± 0.02 0.1 ± 0.03 0.02

MUFA C14:1 0.1 ± 0.02 0.0 ± 0.01 0.1 ± 0.02 0.0 ± 0.02 0.1 ± 0.02 0.0± 0.02 0.03

C16:1n7 1.6 ± 0.58 1.6 ± 1.18 1.4 ± 0.40 1.3 ± 1.12 1.7 ± 0.50 1.2 ± 1.04 1.08

C18:1n9t 0.1ab ± 0.06 0.1a ± 0.02 0.1ab ± 0.06 0.1b ± 0.02 0.11ab ± 0.06 0.1b ± 0.03 0.07

C18:1n9c 24.6a ± 3.84 22.4ab ± 3.45 20.0bc ± 3.15 20.7abc ± 3.8 19.5bc ± 3.41 17.6c ± 5.34 4.60

C20:1n9 0.1abc ± 0.01 0.1c ± 0.01 0.1c ± 0.01 0.1ab ± 0.01 0.1bc ± 0.01 0.1a ± 0.01 0.01

C22:1n9 0.1bc ± 0.02 0.1a ± 0.02 0.1ab ± 0.02 0.1bc ± 0.02 0.1b ± 0.02 0.1c ± 0.02 0.02

C24:1n9 0.2a ± 0.02 0.1ab ± 0.02 0.1ab ± 0.03 0.1b ± 0.03 0.1ab ± 0.02 0.1b ± 0.03 0.03

PUFA C18:2n6t 0.0 ± 0.01 0.0 ± 0.01 0.0 ± 0.01 0.0 ± 0.01 0.0 ± 0.01 0.0 ± 0.01 0.01

C18:2n6c 28.2b ± 2.79 31.2ab ± 2.99 28.4b ± 5.62 34.9a ± 2.11 31.6ab ± 4.25 32.9ab ± 5.72 4.91

C18:3n6 3.2abc ± 0.50 3.8ab ± 0.63 3.0bc ± 0.83 4.0a ± 0.41 3.5abc ± 0.79 3.0c ± 0.63 0.78

C18:3n3 0.3a ± 0.05 0.3b ± 0.05 0.3b ± 0.06 0.3b ± 0.05 0.3b ± 0.04 0.3b ± 0.10 0.08

C20:2 0.5a ± 0.12 0.6a ± 0.06 0.5ab ± 0.08 0.5ab ± 0.16 0.4ab ± 0.10 0.4b ± 0.12 0.13

C20:3n6 3.3bc ± 0.75 2.9c ± 0.47 4.4a ± 0.77 4.2ab ± 0.96 4.3ab ± 0.88 3.9abc ± 1.39 1.08

C20:3n3 0.1 ± 0.05 0.1 ± 0.02 0.1 ± 0.02 0.1 ± 0.03 0.1 ± 0.02 0.1 ± 0.02 0.04

C20:4n6 0.1 ± 0.02 0.1 ± 0.01 0.1 ± 0.02 0.1 ± 0.01 0.1 ± 0.01 0.1 ± 0.02 0.02

C20:5n3 0.3 ± 0.07 0.3 ± 0.06 0.3 ± 0.06 0.3 ± 0.06 0.3 ± 0.06 0.2 ± 0.07 0.07

C22:2 0.1b ±0.01 0.1a ± 0.02 0.1b ± 0.02 0.1b ± 0.01 0.1b ± 0.01 0.1b ± 0.02 0.02

C22:5n3 0.4a ± 0.10 0.3bc ± 0.05 0.3b ± 0.05 0.2bc ± 0.09 0.2c ± 0.06 0.2c ± 0.10 0.09

C22:6n3 1.9ab ± 0.30 1.0d ± 0.21 2.0a ± 0.47 1.5bc ± 0.43 1.7abc ± 0.32 1.4dc ± 0.50 0.46

SFA 34.1 ± 2.75 34.3 ± 5.92 38.2 ± 7.32 31.6 ± 4.76 35.4 ± 6.54 31.9 ± 7.89 7.34

MUFA 27.1a ± 3.78 24.9ab ± 3.12 22.2b ± 1.91 22.3b ± 3.34 22.1b ± 2.82 21.6b ± 4.20 3.89

PUFA 38.7b ± 2.52 40.5b ± 3.70 39.4b ± 5.79 46.0a ± 2.65 42.4ab ± 4.16 43.7ab ± 6.64 5.30

PUFA:SFA 1.1 ± 0.12 1.2 ± 0.33 1.1 ± 0.34 1.5 ± 0.34 1.3 ± 0.40 1.4 ± 0.55 0.43

n-6:n-3 11.2d ± 3.54 20.1a ± 3.16 12.6dc ± 3.76 18.6ab ± 2.98 16.3abc ± 3.38 15.7bc ± 1.13 3.95 Saturated Fatty Acids (SFA); Monounsaturated Fatty Acids (MUFA); Polyunsaturated Fatty Acids (PUFA); Polyunsaturated to Saturated Fatty Acid Ratio (PUFA:SFA); Omega 6 to Omega 3 ratio (n6:n3); Standard Deviation (SD); Least Significant Difference (LSD) abMeans in rows with different superscripts are significantly different at P ≤ 0.05

Correlations

The correlation matrix showing the Pearson correlation coefficients (r) and the P-values for all the

samples are depicted in Table 6.6. A principal component analysis (PCA) bi-plot of the sensory,


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physical and proximate data is illustrated in Fig. 6.1a and demonstrates the correlations between

the different attributes. The combination of the two factors F1 and F2 explained 31.86% of the total

variance of which F1 and F2 explained 18.75% and 13.10%, respectively. The PCA plot seems to

indicate that there were no definite trends between any of the treatments, although there was a

slight trend where BI and BFR are situated at the top half of the plot, and KI and KFR are situated

at the bottom half of the plot.

The DA plot of the sensory, physical and proximate data is illustrated in Fig. 6.1b. The DA

was used to visualize the observations and to analyse the differences between groups of data in

order to see the relationship between groups. The combination of the two factors F1 and F2

explained 80.91% of the total variance of which F1 and F2 explained 52.30% and 28.61%,

respectively. The DA plot indicates, and this corresponds with what is seen in the PCA, that the

treatments are separated by genotype rather than production system, even though the genotypes

are grouped and overlap with each other, with the exception of BFR. This overlapping again

indicates that the treatments were very similar in terms of meat quality and barely distinguishable.


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Figure 6.1 (a) Principal component analysis bi-plot of sensory attributes, physical characteristics, proximate analysis and fatty acid composition

of cooked chicken breast as affected by genotype and production system; (b) Discriminant analysis plot of sensory attributes, physical

characteristics, proximate analysis and fatty acid composition of cooked chicken breast as affected by genotype and production system.

(BI – Broiler intensive; BFR – Broiler free range; HI – Ross X Potchefstroom Koekoek hybrid intensive; HFR – Ross X Potchefstroom Koekoek

hybrid free range; KI – Potchefstroom Koekoek intensive; KFR – Potchefstroom Koekoek free range)

BFR1

BFR2 BFR3

BFR4

BFR5 BFR6

BI1

BI2

BI3 BI4

BI5

BI6

KFR1 KFR2

KFR3

KFR4 KFR5

KFR6 KI1

KI2

KI3 KI4

KI5

KI6

RKFR1

RKFR2

RKFR3

RKFR4

RKFR5

RKFR6

RKI1

RKI2

RKI3

RKI4

RKI5

RKI6 ChickenAroma

InitialJuiciness

ChickenFlavour

SustainedJuiciness

Tenderness

Residue

pH

%Driploss %Cookingloss

WHC

ShearForce %Moist

%Ash

%Fat

%Protein

C14:0

C15:0 C16:0

C18:0

C20:0

C21:0

C22:0

C24:0

C14:1

C16:1

C18:1n9c

C18:1n9t

C20:1

C22:1n9

C24:1

C18:2n6c

C18:2n6t

C18:3n6

C18:3n3 C20:2

C20:3n6

C20:3n3

C20:4n6

C20:5n3 C22:2

C22:5n3

C22:6n3

SFA

MUFA

PUFA

PUFA:SFA n-6:n-3

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

14

-20 -15 -10 -5 0 5 10 15 20

F2 (1

3.10

%)

F1 (18.75 %)

Biplot (axes F1 and F2: 31.86 %)

BFR BI

KFR

KI

RKFR

RKI

-6

-4

-2

0

2

4

6

-6 -4 -2 0 2 4 6 8

F2 (2

8.61

%)

F1 (52.30 %)

Observations (axes F1 and F2: 80.91 %)

(a) (b)


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Table 6.6 Correlation matrix showing the Pearson correlation coefficients (r) and the P-values for all the samples Variables 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

1.Chicken A 1 0.043 0.504 0.254 0.361 -0.197 0.274 0.033 0.101 -0.166 -0.055 0.206 0.363 -0.157 -0.056 0.046 0.098 0 0.804 0.002 0.135 0.031 0.250 0.106 0.850 0.558 0.333 0.749 0.227 0.030 0.361 0.746 0.791 0.568

2.Initial J 0.043 1 0.179 0.165 0.032 -0.169 0.063 0.113 0.191 -0.013 0.036 0.472 0.058 -0.421 -0.175 -0.332 0.175 0.804 0 0.297 0.335 0.851 0.324 0.717 0.512 0.263 0.941 0.835 0.004 0.736 0.011 0.306 0.048 0.306

3.Chicken F 0.504 0.179 1 0.700 0.545 -0.536 0.232 -0.072 0.164 -0.310 -0.081 0.102 0.279 -0.166 0.088 -0.272 0.244 0.002 0.297 0 < 0.0001 0.001 0.001 0.173 0.678 0.340 0.065 0.640 0.553 0.100 0.334 0.609 0.109 0.152

4.Sustained J 0.254 0.165 0.700 1 0.716 -0.659 0.162 -0.232 0.053 -0.045 -0.171 -0.003 0.084 -0.214 0.240 -0.284 0.360 0.135 0.335 < 0.0001 0 < 0.0001 < 0.0001 0.345 0.173 0.760 0.796 0.320 0.988 0.628 0.210 0.159 0.093 0.031

5.Tenderness 0.361 0.032 0.545 0.716 1 -0.678 0.190 -0.112 0.054 0.162 -0.133 -0.040 0.204 -0.074 0.104 -0.225 0.136 0.031 0.851 0.001 < 0.0001 0 < 0.0001 0.268 0.514 0.756 0.346 0.441 0.815 0.232 0.669 0.546 0.187 0.430

6.Residue -0.197 -0.169 -0.536 -0.659 -0.678 1 -0.338 0.108 -0.080 0.105 0.006 0.069 -0.103 0.121 -0.216 0.298 -0.268 0.250 0.324 0.001 < 0.0001 < 0.0001 0 0.044 0.529 0.644 0.542 0.971 0.690 0.550 0.483 0.206 0.078 0.113

7.pH 0.274 0.063 0.232 0.162 0.190 -0.338 1 -0.186 -0.161 -0.048 0.090 0.091 0.239 -0.072 -0.025 0.021 0.157 0.106 0.717 0.173 0.345 0.268 0.044 0 0.278 0.349 0.779 0.603 0.596 0.161 0.678 0.886 0.901 0.362

8.%Driploss 0.033 0.113 -0.072 -0.232 -0.112 0.108 -0.186 1 -0.073 0.080 0.154 0.104 0.396 0.256 -0.270 0.176 -0.027 0.850 0.512 0.678 0.173 0.514 0.529 0.278 0 0.671 0.644 0.370 0.545 0.017 0.131 0.111 0.304 0.878

9.%Cookingloss 0.101 0.191 0.164 0.053 0.054 -0.080 -0.161 -0.073 1 -0.218 0.338 -0.298 0.184 0.335 0.126 -0.146 0.001 0.558 0.263 0.340 0.760 0.756 0.644 0.349 0.671 0 0.202 0.044 0.078 0.282 0.046 0.463 0.395 0.995

10.WHC -0.166 -0.013 -0.310 -0.045 0.162 0.105 -0.048 0.080 -0.218 1 -0.018 0.315 0.072 0.145 -0.458 0.177 -0.008 0.333 0.941 0.065 0.796 0.346 0.542 0.779 0.644 0.202 0 0.916 0.062 0.676 0.400 0.005 0.301 0.964

11.ShearForce -0.055 0.036 -0.081 -0.171 -0.133 0.006 0.090 0.154 0.338 -0.018 1 0.085 0.023 0.247 -0.255 -0.015 -0.138 0.749 0.835 0.640 0.320 0.441 0.971 0.603 0.370 0.044 0.916 0 0.621 0.894 0.146 0.133 0.929 0.421

12.%Moist 0.206 0.472 0.102 -0.003 -0.040 0.069 0.091 0.104 -0.298 0.315 0.085 1 -0.099 -0.366 -0.752 0.041 0.100 0.227 0.004 0.553 0.988 0.815 0.690 0.596 0.545 0.078 0.062 0.621 0 0.565 0.028 < 0.0001 0.811 0.560

13.%Ash 0.363 0.058 0.279 0.084 0.204 -0.103 0.239 0.396 0.184 0.072 0.023 -0.099 1 0.259 -0.009 0.297 0.002 0.030 0.736 0.100 0.628 0.232 0.550 0.161 0.017 0.282 0.676 0.894 0.565 0 0.127 0.959 0.079 0.991

14.%Fat -0.157 -0.421 -0.166 -0.214 -0.074 0.121 -0.072 0.256 0.335 0.145 0.247 -0.366 0.259 1 -0.284 0.313 -0.216 0.361 0.011 0.334 0.210 0.669 0.483 0.678 0.131 0.046 0.400 0.146 0.028 0.127 0 0.094 0.063 0.206

15.%Protein -0.056 -0.175 0.088 0.240 0.104 -0.216 -0.025 -0.270 0.126 -0.458 -0.255 -0.752 -0.009 -0.284 1 -0.272 0.047 0.746 0.306 0.609 0.159 0.546 0.206 0.886 0.111 0.463 0.005 0.133 < 0.0001 0.959 0.094 0 0.109 0.786

16.MUFA 0.046 -0.332 -0.272 -0.284 -0.225 0.298 0.021 0.176 -0.146 0.177 -0.015 0.041 0.297 0.313 -0.272 1 -0.399 0.791 0.048 0.109 0.093 0.187 0.078 0.901 0.304 0.395 0.301 0.929 0.811 0.079 0.063 0.109 0 0.016

17.PUFA 0.098 0.175 0.244 0.360 0.136 -0.268 0.157 -0.027 0.001 -0.008 -0.138 0.100 0.002 -0.216 0.047 -0.399 1 0.568 0.306 0.152 0.031 0.430 0.113 0.362 0.878 0.995 0.964 0.421 0.560 0.991 0.206 0.786 0.016 0

The numbers in the first row correlates with the numbers of the attributes in the first column. The letters following the attribute descriptors “A”, “F”, and “J” refers to aroma, flavour and juiciness respectively. The first row of each attribute shows the Pearson correlation coefficient (r) and the second row of each attribute shows the P-value. All the values in bold are significant at a level of P ≤ 0.05.


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DISCUSSION

There are many factors such as production system, genotype, age, stocking density, lighting,

temperature and diet that may well have an effect on the overall quality of chicken breasts.

Therefore this experiment was designed to limit the number of factors to production system and

genotype. However, it is well known that genotype and production system effects growth rate and

therefore the chickens were slaughtered at different ages but at more or less the same weight in

order to compensate for these effects. Even so, the Potchefstroom Koekoek still grew slower than

both the hybrids and broiler gentypes and as a result lighter chickens were slaughtered. It is

argued though that the difference in carcass weight would have a smaller effect than production

system or genotype on the quality attributes.

Effect of genotype

Tenderness is the ease of shearing, cutting or grounding meat during mastication and consumption

(Gillespie, 1960; Forrest et al., 1975). This attribute is considered to be the most important by

consumers and the main driving force for the final approval of poultry meat (Fletcher, 2002;

Boleman et al., 1997). In this study, no correlation was found between sensory tenderness and

instrumental tenderness (shear force) (Table 6.6). However, a strong negative correlation between

sensory tenderness and residue (Table 6.6) (Fig. 6.1a) was found indicating that a tender meat

sample resulted in less residue.

For genotype, there was no correlation between tenderness and shear force. However,

there might be a trend for Broiler (P = 0.0545; Table 6.2) to measure higher for shear force than

Koekoek and Hybrid resulting in BI and BFR being more closely associated with shear force (Fig.

6.1a). The panel also scored the Broiler less tender than Koekoek and Hybrid (Table 6.2).

Tenderness is affected by the maturity of connected tissue, as well as the contractile state of the

myofibrillar proteins (Fletcher, 2002). However, it was expected that the slower growing birds

would be less tender than the fast growing birds, since the former were older in age and should

have a higher concentration of mature collagen cross linkages at the time of slaughter (Fletcher,

2002). In addition, the Broilers had a higher intramuscular fat (%) content than the other two

genotypes (Table 6.4) and previous studies on chicken and duck showed that a higher fat content

is associated with higher meat tenderness (Zhao et al., 2007; Chartrin et al., 2006). This study’s

results do not agree with Castellini et al. (2002b), Wattanachant et al. (2004) and Fanatico et al.

(2005) where the meat of faster growing chicken genotypes or young birds were more tender than

that of slow growing or older chicken genotypes. However, results from Farmer et al. (1997),

Kishowar et al. (2005); Fanatico et al. (2006, 2007) and Husak et al. (2008) showed that breast

meat from slower growing birds were more tender than fast growing birds. This phenomenon

could be due to muscle fibre size. It is generally known that the latter is associated with genotype

and can influence the meat tenderness positively or negatively. Muscle fibres of fast growing birds


120

are more numerous and have a greater diameter than those found in slow growing birds. Broilers

are selected for their fast growth, resulting in extreme hypertrophy of muscle fibres which is an

indicator of poor meat quality and less tender meat (Fanatico et al., 2007). Another reason for the

difference in tenderness could be due to the reduced proteolytic activity of modern fast growing

chicken lines to produce bigger muscle mass. This reduced proteolytic activity leads to less

tenderization of the meat during post mortem proteolysis (Dransfield & Sosnicki, 1999).

In this study there was a positive correlation (Table 6.6) between shear force and cooking

loss (%). Indicating that when a meat sample had an increased cooking loss (%), a decrease in

tenderness could be expected, this could be the result of concentration of collagen fibres, etc. due

to the moisture loss experienced in the meat. In this study, Broilers had a higher (P ≤ 0.05)

cooking loss (Table 6.3; Fig. 6.1a) than Hybrid and Koekoek genotypes. The amount of moisture

present in meat causes a dilution effect of muscle fibres present in a specific area (Thomas et al.,

2004). It can be assumed that when a piece of chicken meat is less juicy or dry, the tougher the

meat will be and the more residue the meat will have. This assumption is further substantiated by

the strong positive correlation between sustained juiciness and tenderness (Table 6.6) and the

strong negative correlation between sustained juiciness and residue (Table 6.6). This is also

illustrated in the PCA bi-plot (Fig. 1a) where residue is situated on the opposite side of the plot to

initial juiciness, sustained juiciness and tenderness.

Muscle pH is one of the most important meat quality characteristics, because of its effect on

the meat texture, water holding capacity (WHC), cooking loss, juiciness, microbial stability and/or

shelf-life and colour (Fletcher, 1999; Aberle et al., 2001; Honikel, 2004). In this study genotype

had no effect (P > 0.05) on the pH of the meat, therefore no genotype effect would be expected on

the cooking loss, WHC, sustained- and initial juiciness.

Initial juiciness in meat is defined as the moisture released during mastication, whereas the

stimulation of saliva secretion due to the presence of intramuscular fat is defined as sustained

juiciness (Lawrie & Ledward, 2006). According to Offer and Trinick (1983) the initial juiciness and

WHC of meat is positively correlated, consequently if the WHC is poor, the meat will lack juiciness.

WHC gives an indication of the amount of water present in the meat following the cooking process.

The latter causes moisture loss which results in a significant increase in in the intramuscular fat

(%) content of the cooked meat compared to the raw meat, typically meat with a higher cooking

loss will have a higher intramuscular fat (%) content (Alfaia et al., 2010). It is important to keep in

mind that these chicken meat samples were not enhanced with added water, salt and phosphates

to which consumers are familiar with, nor were the samples prepared with ingredients such as salt

or any other seasoning that may stimulate saliva secretion and thus give an impression of

juiciness.

There were no differences (P > 0.05) between sustained juiciness and initial juiciness

(Table 6.2) for the effect of genotype within a production system for any of the chicken samples. It

was expected that the faster growing birds (Broiler) would be more juicy, since they had


121

significantly higher (P ≤ 0.05) intramuscular fat (%) content (Table 6.4), the latter normally

contributes to the juiciness (Fanatico et al., 2005). This would also explain why no correlation

(Table 6.6) was found between sustained juiciness and high intramuscular fat (%) content (Fig 1a).

This study indicated that there was a genotype effect for percentage cooking loss; KI

scored lower and significantly different (P ≤ 0.05) from BI (Table 6.3). This result was unexpected,

since there was no difference (P > 0.05) in the pH (Table 6.3) for these treatments. There is no

explanation for this phenomenon, and further research is required. It was also expected that the

slower growing Hybrid and Koekoek would have a higher cooking loss, since a low pH is caused by

the higher activity and stress experienced by these birds (Castellini et al., 2002a; Lonergan et al.,

2003; Fanatico et al., 2005; Lawrie & Ledward, 2006). There was also a genotype difference

(P ≤ 0.05) between HFR and BFR for the % drip loss. This difference in drip loss could be

explained by the size of the breast fillets of Hybrid which are smaller and thinner in dimension

(Chapter 3) compared to Broiler, and therefore have relatively more surface area in relation to

muscle mass and exposure to the air, which likely caused the higher drip loss (Fanatico et al.,

2005). The correlations between the attributes showed that there was a negative correlation

between initial juiciness and intramuscular fat (%) (Table 6.6) and a positive correlation between

cooking loss and intramuscular fat (%) (Table 6.6) and initial juiciness and percentage moisture

(Table 6.6). This is further illustrated and confirmed in the PCA bi-plot (Fig. 1a) where percentage

fat is situated on the opposite side of the plot to sustained and initial juiciness.

Flavour in meat is the third most important characteristic, after appearance and tenderness,

perceived by the consumer (King et al., 2009). The flavour of meat is a combination of taste and

smell and is formed by chemical reactions during cooking (Mottram, 1998 Farmer, 1999). Meat

flavour and aroma increases with animal age, therefore slower growing birds harvested at an older

age are expected to have meat with a more intense flavour than conventional broilers (Aberle et

al., 2001; Elmore & Mottram, 2009). This increased flavour could be due to the fact that older birds

contain higher concentrations of nucleotides in muscles, which degrade to inosinic acid and

hypoxanthine after death; two chemical compounds known to be associated with meat flavour

(Aberle et al., 2001). The Hybrid chicken scored higher (P ≤ 0.05) in flavour and aroma than the

Broiler and Koekoek genotypes (Table 6.2). This is surprising, since a more intense flavour and

aroma is generally associated with older birds, and therefore the Koekoek was expected to have

the strongest flavour.

Flavour is also correlated to the intramuscular fat content of meat; therefore the presence of

a higher fat content (%) will give a more flavoursome meat (Lawrie & Ledward, 2006). BI scored

higher (P ≤ 0.05) in intramuscular fat (%) content (Table 6.4) than HI, consequently the Broiler

genotype were also expected to give a more flavoursome meat. Gordon and Charles (2002)

reported that flavour precursors (flavour development) are only deposited in the muscle after the

growth inflection point (the age at which gain is at its maximum). In this study it is possible that the

Hybrid were at a more mature stage of development (as a function of their adult weight) than the


122

Koekoek chickens, which did not reach their inflection point before slaughter. It is also important to

keep in mind that the breast meat was cooked with no salt added and the skin removed, as these

would have enhanced the flavour. The findings of this study agree with those of Fanatico et al.

(2007) and Touraille et al. (1981) where the meat of faster growing birds had more flavour than

slower growing birds harvested at different ages.

According to Harkes and Begemann (1974), thermal oxidation of n-6 and n-3 fatty acids,

especially arachidonic, linoleic and oleic acids, in meat are responsible for the characteristically

cooked chicken flavour. These fatty acids break down during heating and give aldehyde

compounds that are more unsaturated and reactive in further developments. These compounds

then react with Maillard precursors and appear to catalyse the breakdown of more saturated fatty

acids to affect, as well as contribute to, the meat flavour (Imafidon & Spanier, 1994, Elmore et al.,

1999). Enser (1999) reported that linoleic acid is responsible for the presence of a mild chicken

flavour in meat. This fatty acid dominates over the other fatty acids in the fatty acid profile (Table

6.5). In this study, however, a negative correlation (r = -0.08832; P ≤ 0.05) was found between

chicken flavour and α-linoleic acid (C18:2n6c). A possible explanation for this phenomenon could

be that during the trained panel sessions while defining the attribute chicken flavour, a strong

chicken flavour was actually defined and not a mild chicken flavour, which α-linoleic acid

represents. Chicken flavour did, however, correlated positively with total SFA (Table 6.6) and

palmitic acid (C16:0) (Table 6.6). Therefore, it can be speculated that palmitic acid may be

responsible for the stronger chicken flavour present in Hybrid. Chicken aroma also correlated

positively with SFA (Table 6.6) and myristic (C14:0) (Table 6.6), pentadecylic (C15:0) (Table 6.6),

palmitic (C16:0) (Table 6.6) acids. These correlations suggest that these fatty acids may be

involved in the formation of the chicken flavour and aroma. Another possible explanation for the

enhanced chicken flavour and aroma, especially for Hybrid, is that during cooking, the n-6 and n-3

fatty acids reacted with other flavour precursors or compounds forming aldehydes which could

have contributed to the chicken flavour and aroma. This warrants further research to help clarify or

explain the factors contributing to the stronger chicken flavour. Feed composition plays a very important role in the fatty acid composition of monogastric

animals. All the chickens in this study was given the same feed composition (Chapter 3; Table 6.1)

which was predominately a maize diet (~60%) with soybean full fat (~17%) for starter and grower

diets with an increased soybean (~36%) for the finisher diet and added fish meal (~10%). The IMF

content and the main fatty acids present in bird fat are palmitic (C16:0), palmitoleic (C16:1), oleic

(C18:1), stearic (C18:0) and linoleic (C18:2) acids with oleic (C18:1) acid being the highest in

chicken meat (Gunstone & Russell, 1954; Enser, 1999; Lawrie & Ledward, 2006). Similar results

were found in this study (Table 6.5). There was a trend in this study for the Broiler birds to contain

higher (P ≤ 0.05) oleic acid (C18:1n9c) than the Hybrid and Koekoek genotypes. This oleic

originated from the soybean in the feed which is high in oleic acid (Tat et al., 2007). It is possible


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that the Broiler genotype utilises soybean better than the Hybrid and Koekoek genotypes to create

oleic acid in the meat.

Fatty acid composition is described by two important ratios PUFA:SFA and n-6:n-3 (Enser

et al., 1998). Raes et al. (2004) suggest that a PUFA:SFA of > 0.45 and a n-6:n-3 ratio of <4

contributes to the healthiness of meat products. In this study there was an overall trend for the

Broiler to score higher (P ≤ 0.05) in SFA and lower (P ≤ 0.05) in PUFA than Hybrid and Koekoek.

However this did not affect the overall PUFA:SFA ratio and this ratio, for all the chicken samples,

falls within the recommended value to promote healthiness. The n-6:n-3 ratio was also not

affected (P<0.05) by genotype.


The effect of production system on the sensory and physical attributes, as well as chemical and

fatty acid composition was less substantial in comparison to that of genotype.

According to Tables 6.1 and 6.2, production system did not have any effect (P > 0.05) on

the sensory tenderness and instrumental shear force of chicken meat. It was expected that the

chickens who had access to an outdoor area or was exposed to free range rearing to have tougher

meat, due to increased intramuscular collagen caused by the birds having a higher level of

physical activity (Lewis et al., 2005). Physical activity or exercise may cause strengthening of the

connective tissue and alter the fibre type size, resulting in tougher meat (Aberle et al., 2001). It

has also been shown that birds reared outdoors have more firm meat than birds reared indoors

(Castellini et al., 2002a). This study’s results agree with Fanatico et al. (2007) where production

system had no effect on meat tenderness. In some previous studies, free range meat was even

found to be more tender than indoor birds, although this was only noted for fast growing birds

(Fanatico et al., 2005). It is also important to remember that in this study only the breast meat of

the three chicken genotypes was evaluated for tenderness. The breast muscle does not get as

much exercise as the thigh or leg, which could also have led to less toughening of the breast meat

in the free range reared birds.

Offer and Trinick (1983) concluded that the initial juiciness of meat is positively correlated

with the WHC of meat, which is determined by the ultimate pH of the muscle. In this study there

was a higher (P ≤ 0.05) ultimate pH between BI and BFR (Table 6.3), although no difference

(P > 0.05) was detected in the juiciness of these samples (Table 6.2). According to literature it was

expected that the free range samples would be less juicy, since a lower pH was likely due to lower

stress conditions and more consumption of glycogen before slaughter (Enfalt et al., 1997; Castellini

et al., 2002a; Fanatico et al., 2007; Wang et al., 2009).

There was also a production system effect (P ≤ 0.05) on the intramuscular fat (%) content

of the HI and HFR. However, it did not have any effect on the juiciness content of these samples.

These results agree with Kishowar et al. (2005) and Husak et al. (2008) where no difference in

juiciness was found between intensive and free range reared birds. This study also indicates that


124

the correlation between WHC with initial juiciness and sustained juiciness is inconclusive (Table

6.6).

Production system within a genotype did not have an effect (P > 0.05) on chicken flavour

and aroma (Table 6.2). Similar results were expected in this study to those of Touraille (1981) and

Fanatico et al. (2006; 2007), where outdoor birds slaughtered at different ages had a stronger

flavour due to more n-3 fatty acids being present in the meat. Chickens are monogastric animals,

therefore the fatty acid composition of the feed will directly reflect in the meat muscle (Wood &

Enser, 1997). These n-3 fatty acids originate from green forage and grass rich in α-Linolenic acid

(C18:3n3) and will result in high levels of the latter being present in the muscle tissue of chickens

that feed on grass (Enser et al. 1998, Pegg & Shahidi, 2004) In this study, the α-Linolenic acid

content (Table 6.5) of the free range animals did not differ from the intensively reared animals.

Forage did not play a role in the fatty acid composition of the outdoor birds as it was noted that the

Hybrid hybrids and Koekoek chickens had consumed all the foliage within the first week of outdoor

access. The chickens in this study were fed the same maize based diet (Chapter 4; Table 4.1).

The latter is generally considered to be of a more saturated nature with higher palmitic acid

(C16:1), oleic acid (C18:1) and linoleic acid (C18:2n6) content and lower PUFA compared to grass

or forage based diets. Together, palmitic acid, oleic acid and linoleic acid comprised ~50% of the

total fatty acids present in the cooked breasts of all the chicken samples (Table 6.5).

As mentioned the two important ratios to consider in the fatty acid analysis are the

PUFA:SFA and the n-6:n-3 ratios. In this study there was no effect (P<0.05) of production system

on the PUFA:SFA ratio, but rearing Broiler and Hybrid in a free range environment caused the n-

6:n-3 ratio to increase significantly (P ≤ 0.05).

A few studies have shown that free range chicken meat has a lower n-6:n-3 ratio, making it

a more favourable product than intensive chicken meat and aids to human health (Castellini et al.,

2002a; Jahan & Paterson, 2007; Husak et al., 2008). As mentioned, it was expected that the free

range chicken meat products would contain more n-3 PUFA, since the major food source should

be pasture, which is a good source of α-linolenic acid (18:3n-3) (Ponte et al., 2008; Jahan &

Paterson, 2007). In this study this was not the case, resulting in the n-6:n-3 of all the meat

samples being above the recommended value (4); in fact the BFR and HFR had even higher

(P ≤ 0.05) n-6:n-3 ratios (Table 6.5) than the BI and HI. The linoleic acid (C18:2n6c) is responsible

for the high n-6 content in the meat and originated from the high maize diet (Storry & Rook, 1965).

A possible reason for the higher n-6:n-3 ratio, could be that the free range birds used the EPA

(20:5n3) and DHA (22:6n3), during stressful times as to support their immune system, rather than

depositing it in the meat as described in Chaper 4 (Cook et al., 1993). The same results were also

found by Jahan et al. (2004) where extensive chicken meat contained higher n-6:n-3 ratios. It is

important to remember that free range birds are usually given feed with a different composition

than the normal conventional (intensive reared) chickens; these diets would be more suitable for

free range rearing and might affect the fatty acid profile of the meat differently.


125

CONCLUSIONS

The aim of this study was to determine the sensory, physical, proximate and fatty acid quality

characteristics of chicken breasts from three different genotypes (Broiler, Hybrid hybrid and

Potchefstroom Koekoek) reared in intensive or free range production systems in order to establish

if there are any differences in the meat quality.

The results indicate that the effect of production system within a specific genotype plays no

significant role on the meat quality characteristics and that the differences in meat quality are

mainly due to the genotype. Meat of the faster growing chicken genotypes or younger birds

(Broiler) was less tender (higher shear force) than the meat of slow growing or older chicken

genotypes (Hybrid and Koekoek). The Hybrid chicken genotype scored significantly higher

(P ≤ 0.05) in both flavour and aroma than the Broiler and Koekoek genotypes. This phenomenon

could be ascribed to the n-6 and n-3 fatty acids and other flavour precursor’s forming aldehydes

during cooking or palmitic acid (C16:0) that could have contributed to the chicken flavour. This,

however, would need further research since the chickens had all received the same diet and

consequently the reasons for the differences in fatty acid composition is unknown. The Hybrid also

had a higher percentage drip loss (P ≤ 0.05) than Broiler. This could be explained by the smaller

and thinner dimension of the Hybrid breast fillet compared to the Broiler fillet.

Although some attributes differed (P ≤ 0.05) from each other, the question arises whether

these minor differences are of such a magnitude that consumers could identify any differences

between the different treatments. It also seems that the Hybrid genotype will be the more suitable

for free range rearing than Broiler in terms of flavour and aroma. However, whether this hybrid

would be the more economical choice, due to differences in feed conversion ratio, growth rate and

yield, (Chapter 3) than the commercial genotype requires further research.

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CHAPTER 7

A SOUTH AFRICAN PERCEPTION OF CHICKEN MEAT

ABSTRACT

Modern consumers are health conscious and are shifting to more naturally produced products such

as free range chicken. Commercial broilers strains are not suitable for free range rearing and an

alternative genotype is needed that will suite the South African market without compromising on

meat quality. The main objective of this study was to investigate the impact of genotype and

production system on the consumer perception and degree of linking of cooked chicken breast

(pectolaris major) meat. The consumers favoured Hybrid hybrid more than the normal Broiler

genotype. Consumers prefer the overall flavour of intensive reared chicken when tested blind, but

when information is given about the rearing system they lean towards free range reared chicken.

The main drivers of chicken meat liking were found to be juiciness, tenderness, chicken aroma and

chicken flavour. Consumer’s perception and opinions are overall positive towards free range

reared products and they believe it is better than intensive reared chicken. Three clusters of

consumers were also identified: two groups of consumers whom will stay loyal to either free range

or intensive reared chicken meat and the third that prefers both free range and intensive reared

meat.

Keywords: Broiler, Hybrid hybrid, Consumer perception, Degree of liking.

INTRODUCTION

The modern consumer generally tends to be more aware of the health and nutritional value of the

food consumed, is more conscious of animal welfare, desires more naturally produced products

and supports a more sustainable way of farming (Sundrum, 2001). Needless to say, together with

these requirements, the consumer still expects a high standard regarding the flavour of the food

(Hoffman & Cawthorn, 2012). Studying the preferences and attitudes towards a specific type of

product, as well as the information about consumers’ age, gender, socio-demographics, and habits

may be extremely relevant for product development, marketing endeavours and ultimately for

increasing sales (Thybo et al., 2004). Therefore producers need to understand consumer

behaviour and perceptions that drive the consumers’ attitude towards purchasing a product. The

challenges the chicken farmers face are daunting and producers need to comply with the

consumers’ demand and at the same time generate a fair profit.

In the meat market, the interest of the consumer has grown towards quality aspects, rather

than just quantity; this mind shift of the consumer has provided opportunities for market


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segmentation of specialty products, such as free range and organic. Although consumers expect a

higher degree of welfare in free range chickens, this is only true if slow-growing chicken strains are

used (Castellini et al., 2008; Van de Weerd et al., 2009). In South Africa, the normal fast growing

commercial broiler is currently used for both free range and intensive production. These chickens

reach market weight as early as 28 - 32 days under the optimal intensive production system. As a

result of genetic selection, for fast growing animals, their behavior has changed to reduced kinetic

activity (Schütz & Jensen, 2001; Branciari et al., 2009). Therefore, broilers have a habit of staying

indoors, being dormant and less active (Smith & Carpernter, 1970; Lewis et al., 2005). This rapid

growth has also led to concerns about animal welfare, since more leg disorders and a higher

mortality rate occur. On the other hand, extensive production practices leads to higher production

costs and lower turn over, causing the products to be more expensive than intensive production

products. The question arises whether the consumer is willing to pay for a quality product?

According to Thompson (1998), Bennett et al. (2002), Du Toit and Crafford (2003), Napolitano et

al. (2010), Van Loo et al. (2011) and Janssen & Hamm (2012), consumers are frequently willing to

pay a higher price for certified products. The consumer, who can afford free range and organic

products, is generally a more wealthy, well-educated and traveled person who places value on the

quality aspects of the meat (Martelli, 2009).

As already mentioned, the farmers in South Africa utilize the same fast growing chicken

lines, which has been bred specifically for intensive rearing for their extensive rearing methods.

However, the suitability of these fast-growing broilers, for outdoor production and specialty

markets, has not been extensively researched (Fanatico et al., 2005).

Castellini et al. (2008) reported that only slow-growing chicken strains can completely

benefit from an extensive rearing system and that the fast growing strains are considered slow to

adapt to change. Therefore, a slower growing chicken line is needed, that can adapt to the harsh

conditions of the South African weather, can eat the forage in an extensive production system and

still give the same meat quality as the broiler.

A few studies have been done on consumer perception and attitude towards chicken meat,

as well as their perception on different rearing systems and consumers believe that the meat of

free range chickens are healthier and tastier than birds reared in confinement and their overall

perception is positive towards free range production systems (Verbeke & Viane 1999; Yeung &

Morris, 2001; Harper & Makatouni 2002; Grunert et al, 2004; Greene et al., 2005 as cited by

Fanatico et al., 2005; Fanatico et al., 2007; Castellini et al., 2008; Branciari et al., 2009). In a

consumer study where commercial broilers were compared with organic free range broilers in a

blind tasting, it was reported that although consumers found no differences in breast fillet juiciness,

tenderness, or flavour, consumers did prefer the commercial broiler meat over the organic free-

range broiler meat (Greene et al., 2005 as cited by Fanatico et al., 2005). Such studies have never

been done in a South African environment or on indigenous chickens cross bred with commercial

broilers.


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In view of the above, this study was undertaken to gain information on the consumers’

degree of liking of two different chicken genotypes: Broiler (Cobb 500) and Ross 308 X

Potchefstroom Koekoek reared in intensive and free range environments. The consumers were

also tested for perceptions on the rearing method i.e. intensive or free range of chickens per se.

Correlations between the sensory and consumer data were made in order to determine the drivers

of liking, as well as understanding consumer expectations.



†Two hundred crossbred (Ross 308 roosters X Potchefstroom Koekoek hens) chicks were hatched

at Mariendahl, (33° 51’ 0 S; 18° 49’ 6 0 E) Experimental Farm, Stellenbosch University, situated in

the Western Cape, South Africa. Two hundred one day old Cobb 500 (Broiler) chicks were

purchased from Tydstroom hatchery near Hermon (Western Cape, South Africa) and brought to

Mariendahl. Each chick was vaccinated against infectious bursal disease (IBD) at one day of age

and Newcastle disease at one and 18 days of age. After individual weighing and tagging the one

day old chicks were randomly assigned to two rearing systems; intensive (n = 100 per genotype)

and extensive/free range (n = 100). Genotypes were maintained separately. All chickens were fed

ad libitum the same complete commercial type diet consisting of a starter, grower and finisher feed

(Table 7.1). Feed was allocated to the chicks at a volume of 900 g starter, 1200 g grower and

finisher until slaughter.

Intensive production system

At day one of age, the BI, HI and KI chicks were placed into a bioassay unit (intensive system).

The chicks were grouped according to genotype for each treatment. This unit comprises of a

temperature controlled room equipped with wire cages (0.3 x 0.25 m; 53 birds/m2). Management

practices described by ROSS International were followed (Aviagen, 2009). Artificial lighting was

provided at a pattern of 16 h of light altering with 8 h of darkness. Ventilation in the house was set

to provide a minimum of six air changes per hour. At the age of 14 days, the chicks were moved to

a chicken house equipped with wire cages (0.9 x 0.6 m; 14 birds/m2) (Fig. 4.1a), each containing a

tube feeder and two nipple drinkers. Again the chicks were grouped according to genotype. The

temperature in the room was controlled and decreased as they grew from 33°C to 15°C and

ventilation in the house was set to provide a minimum of six air changes per hour. Artificial lighting

was provided at a pattern of 16 h of light alternating with 8 h of darkness.

†Note that in this chapter the Koekoek genotype was not evaluated as in the previous chapters, thus the description of the experimental birds is described again.


134

Table 7.1 Ingredient (%) and calculated nutrient composition of commercial diets fed to intensively

and extensively reared chickens

Ingredients (%) Starter Grower Finisher

Maize 61.59 65.76 59.66

Fish meal 65 9.79 10.00 -

Soybean full fat 16.85 18.84 36.13

Soybean 46 8.87 3.00 -

L-lysine HCL 0.27 - 0.20

DL methionine 0.27 0.21 0.31

L-Threonine 0.14 0.05 0.11

Vitamin + mineral premix 0.15 0.15 0.15

Limestone 0.80 1.01 1.58

Salt - 0.05 0.25

Monocalcium phosphate 0.84 0.75 1.45

Sodium bicarbonate 0.43 0.17 0.17

Total 100.00 100.00 100.00

Calculated nutrient composition

AMEn* chick 12.50 12.90 13.00

Crude protein % 22.54 20.73 18.97

Dry matter % 88.22 88.03 88.20

Lysine % 1.52 1.21 1.17

Methionine% 0.69 0.62 0.59

Crude fat % 6.57 7.03 8.95

Calcium % 0.90 0.96 0.92

Avail. Phosphorus % 0.50 0.48 0.45

*Nitrogen-corrected apparent metabolizable energy value (AMEn)

Extensive production system

The day old BFR, HFR and KFR chicks were placed in small pens (2.7 x 3.5 m) with deep wood

shavings in an indoor chicken house facility. The chicks were grouped according to genotype for

each treatment in the pens. The initial density of each pen was 10.5 birds/m2. Artificial lighting

was provided at a pattern of 16 h of light altering with 8 h of darkness and ventilation in the house

was set to provide a minimum of six air changes per hour. At 21 days of age, the chicks were

moved outside to a larger facility (Fig. 7.1b). This facility was naturally ventilated. The house was

subdivided into two “indoor” pens that opened into two separate yards, which were surrounded by

chicken wire. The “indoor” areas of each pen measured 1.5 x 3.0 m and contained fresh wood

shavings and infrared light heaters that were used to maintain night temperatures above 15°C.

Birds were allowed unlimited access to the “outdoor” area. The “outdoor” area consisted of a

concrete floor area covered with shading (3.0 x 4.5 m) and an open air grassy area (3.0 m x 6.0

m). Each pen measured 3.0 x 12.0 m (2.8 birds/m2). The grassy area was completely covered


135

with natural growing vegetation (mainly kikuyu grass). The outdoor and indoor areas were

provided with automatic drinkers as well as chicken feeders allowing for ad libitum access.

Photoperiod was limited natural daylight (~15 h of daylight and 9 h of darkness). Management

practices described by the SAPA code of practice 2012 under the section free range broiler

production were followed (Anon., 2012b).

Figure 7.1 (a) Intensive production wire cages; (b) Extensive production housing pens.

Slaughtering

At the age of 42 and 56 days respectively, 100 Broiler and Hybrid hybrid chickens with a target

weight range between 2.0 to 2.3 kg were randomly selected and slaughtered, according to

acceptable commercial standards through immobilization by electrical stunning (50-70 volts; 3-5 s),

followed by exsanguination and de-feathering and dressing. After evisceration, the carcasses

were chilled at 4 °C for approximately 12 h. Thereafter the carcasses were transported to the meat

science laboratory at Stellenbosch University. After skinning, the breast muscles were removed by

cutting from the clavicale furcula bone alongside the keel bone, the weight recorded and the meat

vacuum-packed and frozen at -18 °C until analysed further.

Experimental units

The experimental units included four meat treatments which consisted of a Broiler and Hybrid

sample each reared in intensive and free range production systems (n = 4). The consumer

analysis was performed on the cooked right and left breasts of the carcass with three consumers

per breast (Fig. 7.2). The analyses were thus performed on 68 birds. The following acronyms are

used to describe the four different treatments: BI – Broiler intensive; BFR – Broiler free range; HI –

Ross X Potchefstroom Koekoek hybrid intensive; HFR – Ross X Potchefstroom Koekoek hybrid

free range.

(a) (b)


136

Sample preparation

The consumer test was conducted at the sensory research facility of the Food Science

Department, University of Stellenbosch inside a temperature-controlled (21°C) and light-controlled

(artificial daylight) room (AMSA, 1995). The frozen breast samples from each treatment, were

removed from the freezer (-18°C) and defrosted in a refrigerator at 4°C for 12 h prior to the

consumer analysis session. The defrosted samples were removed from the packaging and placed

inside separate marked oven roasting bags (GLAD™). Meat was not salted or seasoned. The

roasting bags with the meat samples were then placed on a stainless steel grid and fitted onto an

oven roasting pan. The samples were placed in an industrial forced convection oven (Hobart),

preheated to 160°C (AMSA, 1995). The meat samples were roasted for 20 min and removed from

the oven. After removal from the roasting bags the samples for each consumer for sample set 1

(served with no information) and sample set 2 (served with information) were cut into 2 x 2 x 2 cm

cubs as illustrated in Fig. 7.2. Consumers were given samples from the same chicken breast for

sample set 1 and sample set 2 to lessen variation within breasts. The samples were then

individually placed into corresponding marked glass ramekins. Before the samples were served to

the consumers for analysis, the ramekins containing the meat samples were placed in a preheated

oven (100°C) and reheated for 10 min where after they were immediately served to the panel.

Figure 7.2 Diagram showing the division of a single chicken breast sample into test samples for

consumers in sample set 1 (no information) and sample set 2 (with information).

Consumer sensory analysis

As a consumer panel can only analyse a limited number of samples, the genotypes broiler and

Hybrid hybrid were chosen for this study. Hundred consumers (n = 100) who regularly consume

chicken meat, between the ages of 18 and 60 were sourced in the Western Cape area, South

Con

sum

er 1

Con

sum

er 2

Con

sum

er 3

Sample

set 1

Sample

set 2

Sample

set 1

Sample

set 1

Sample

set 2 Sample

set 2


137

Africa. The group of consumers were asked to complete a questionnaire (Addendum A)

determining the overall degree of liking of the eating quality, as well as the texture of the chicken

samples using the 9-nine point hedonic scale (Addendum A). Internationally, the nine point

hedonic scale has been studied widely and has been found to be extremely useful in the hedonic

assessment of various foods and beverages on the market. In this test, the consumer is asked to

indicate which term best describes his/her attitude towards the products being tasted using the

scale with the following nine categories (Lawless & Heymann, 2010): 9 = Like extremely; 8 = Like

very much; 7 = Like moderately; 6 = Like slightly; 5 = Neither like nor dislike; 4 = Dislike slightly;

3 = Dislike moderately; 2 = Dislike very much and 1 = Dislike extremely. Consumers were asked

to cleanse their palates with distilled water and water biscuits (Carr, UK) so as to prevent a carry-

over effect between samples.

The questionnaire consisted of a sample set 1 where consumers were not given any

information about the chicken genotype or rearing environment; this test purely tested consumer

preference and degree of liking and eliminated any bias and it was envisaged that it would prevent

any preconceived ideas of the product influencing their answers. In this sample set the samples

were presented in a completely randomised order. In sample set 2, however, consumers were

given information about the rearing system, as well as genotype of the chicken to gain information

about perception and prejudice over a specific product. The purpose of this test was to identify

which products the consumers viewed as acceptable or unacceptable. It is also important to note

that no consumers were asked to explain their choice (Lawless & Heymann, 2010).

Questions relating to socio-demographics of the consumers were also incorporated in the

questionnaire and included: gender, age, race, income, education, current employment and

frequency of consuming chicken products.

Along with the questionnaire about preference of the four chicken meat samples,

consumers were asked to complete a questionnaire where they would indicate their opinion about

free range products and normal conventional or intensive reared chicken by answering “Yes”, “No”,

or “I am not sure”. This test indicates consumer perception or opinion of free range products. A

question was posed to ascertain whether the consumers were aware of the true meaning of the

terms “free range” and “intensive production systems”. Finally the consumers were probed on

factors that might affect their purchasing intent. A nine-point scale ranging from 1 = Not important

to 9 = Extremely important was used to indicate whether specific factors such as price, place of

purchase and rearing method of chickens play would influence the purchasing decision.

Statistical analysis

For the consumer analysis, a randomised complete block design was used, with each consumer

(n = 100) testing the four chicken samples (2 genotypes x 2 rearing methods) in random order

without any information regarding the samples. In the second session, the testing of the samples

was repeated, however, the information pertaining to genotypes and rearing methods was


138

supplied. The model for the consumer experimental design including the consumer effect and the

two factor interactions is indicated by the following equation:

Yijk = µ + Consn +αi + βj + γk + αβij +αγik + βγjk + (α*Cons)in + (β*Cons)jn + (γ*Cons)kn + (αβ*Cons)ijn +

(αγ*Cons)ikn + (βγ*Cons)jkn + εijkn

Where µ is the overall mean, α, β and γ are the main effects for the corresponding design factors

(genotype, rearing method and information, respectively), Cons is the consumer effect and εijkn is

the random error.

The segmentation model including additional consumer demographic information is:

Yijk = µ + Φl + Cons(Φ)ln +αi + βj + γk + αβij +αγik + βγjk + Φ*αil + Φ*βjl + Φ*γkl + Φ*αβijl + Φ*αγikl +

Φ*βγjkl + (α*Cons(Φ))inl + (β*Cons(Φ))jnl + (γ*Cons(Φ))knl + (αβ*Cons(Φ))ijnl + (αγ*Cons(Φ))iknl +

(βγ*Cons(Φ))jknl + εijknl

where Φl represents the demographic effect and Cons(Φ)nl represents the consumer effect within

the demographic effect (Næs et al., 2010).

Analyses of variance (ANOVA) was performed using SAS™ statistical software (Statistical

Analysis System, Version, 9.2, 2006, SAS Institute Inc., CARY, NC, USA), while the multivariate

statistical analysis was performed using XL STAT™ statistical software (Version 2011, Addinsoft,

New York, USA). Student’s t-least significant differences were calculated at the 5% level to

compare preference means for samples, overall and for different demographic groups. A

probability level of 5% was considered significant for all significance tests. Principal component

analysis (PCA) was conducted to investigate the association of preference patterns for the

samples with demographic groupings.

RESULTS AND DISCUSSION

Consumer preference testing of chicken

Relating consumer liking and sensory data

The purpose of this study was to determine the degree of liking of the four chicken variants by

consumers from the Western Cape area, South Africa. The samples were firstly tested blind for

degree of liking (no additional information supplied), thereafter the same four samples were tested

again, this time with added information on the genotype as well as rearing system. Table 7.2

indicates the mean scores of degree of liking of the texture and flavour of the four different chicken

samples within informed and non-informed scenarios, respectively. Table 7.3 indicates the overall


139

mean scores of degree of liking of the texture and flavour of the four different samples. From

Table 7.2 it is clear that HFR from the informed scenario scored the highest degree (P ≤ 0.05) of

liking for both texture and flavour. Also interesting to note from Table 7.2, for the informed

scenario, consumers scored an overall higher degree of liking for the free range samples (BFR and

HFR) than the intensive samples (BI and HI). From Table 7.3 it can be concluded that the

consumers preferred (P ≤ 0.05) the texture and flavour of the Hybrid hybrid more than the Broiler

for both production systems. It would seem that genotype had a higher impact on consumer liking

than production system’. These results are in agreement with that of Fanatico et al. (2007) where

genotype also had a stronger influence than production system in a consumer analysis.

Associations between sensory, physical and chemical attributes as defined in Chapter 5 of

the chicken meat and the consumer data from this chapter were investigated using PCA (Fig. 7.3a,

b). Fig. 7.3a indicates the association of consumer`s degree of liking of the texture of the meat for

both sample sets (with information and no information) and Fig. 7.3b the degree of liking of the

flavour of the meat for both the sample sets (with information and no information). Factor 1 and 2

(F1and F2) of Fig. 7.3a explained 80.35% of the total variance. F1 and F2 of Fig. 7.3b explained

81.67% of the total variance, These PCA bi-plots seem to indicate that there was a trend between

the different treatments, where PC1 divided genotype, with Hybrid hybrid situated on the right hand

side of the plot and Broiler on the left hand side of the plot. On the other hand, PC2 divides

production system with intensive situated on the bottom half of the plot and free range on the top

half of the plot.

From Fig. 7.3a and b it is clear that the consumers preferred the flavour and texture of HI

and HFR more than they would BI and BFR. Sensory descriptors that correlated positively with the

degree of liking were chicken aroma, chicken flavour, tenderness and juiciness. From this it is

clear that the consumers prefer chicken meat that is juicy, tender and has a chicken flavour and

aroma. These findings compare well to work reported by Aaslyng (2009). From Fig. 7.3 it is also

clear that this group of consumers responded less positively to the attributes shear force and

residue.

The results in Fig. 7.3a and 7.3b also showed that the consumers’ preference for a specific

chicken sample differed when tested within non-informed and informed scenarios. In the non-

informed scenario (i.e. tasting the sample blind), consumers preferred the Hybrid intensive sample

and for the informed scenario they preferred the Hybrid free range sample. Guinard et al. (2001)

also found a difference in degree of liking when consumers tasted beer samples informed versus

blind. Our results indicate that consumer perception plays an immense role when it comes to

consumer decision making and is therefore the main reason for change in decision. Consumers

make decisions based on how they perceive free range and intensive products. In our study,

consumers perceived and believe that free range products have a better value (whether it is

healthier – as linked to its chemical composition, especially fatty acids, tastier, leaner or juicier)

than intensive products and therefore scored it a higher.


140

Table 7.2 The mean scores of degree of liking (± SD) of texture and flavour of the four different

chicken samples for when no information was supplied (blind) and when information was

supplied

Sample* Texture Flavour

BI_Info 5.7e ± 1.68 5.8cd ± 1.65

BI_No 5.9cde ± 1.86 6.0bcd ± 1.79

BFR_Info 6.2bc ±1.78 6.1bc ± 1.86

BFR_No 5.8de ± 1.65 5.7d ± 1.67

HI_Info 6.3ab ± 1.78 6.1bcd ± 1.71

HI_No 6.1bcd ± 1.41 6.2ab ± 1.70

HFR_Info 6.6a ± 1.50 6.6a ± 1.61

HFR_No 6.1bcde ± 1.78 6.3ab ± 1.66

LSD 0.39 0.38

Standard Deviation (SD); Least Significant Difference (LSD) abMeans in columns with different superscripts are significantly different at P ≤ 0.05

*BI_Info – Broiler intensive with information; BI_No – Broiler intensive with no information; BFR_Info – Broiler free range with information; BFR_No – Broiler free range with no information; HI_Info – Ross X Potchefstroom Koekoek hybrid intensive with information; HI_No – Ross X Potchefstroom Koekoek hybrid intensive with no information; HFR_Info – Ross X Potchefstroom Koekoek hybrid free range with information; HFR_No – Ross X Potchefstroom Koekoek hybrid free range with no information

Table 7.3 The overall mean scores of degree of liking (± SD) of texture and flavour of the four

different chicken samples

Sample* Texture Flavour

BI 5.9c ± 1.72 5.9b ± 1.77

BFR 5.8bc ± 1.76 5.9b ± 1.72

HI 6.3a ±1.6 6.4ab ±1.64

HFR 6.2ab ± 1.61 6.2a ± 1.70

LSD 1.96 0.31

Standard Deviation (SD); Least Significant Difference (LSD) abMeans in columns with different superscripts are significantly different at P ≤ 0.05

*BI – Broiler intensive; BFR – Broiler free range; HI – Ross X Potchefstroom Koekoek hybrid intensive; HFR – Ross X Potchefstroom Koekoek hybrid free range


141

Figure 7.3 (a) Principal component analysis (PCA) bi-plot indicating the position of the sensory attributes (indicated in red), in relation to the four

chicken meat samples (indicated in capital letters and green) and the degree of liking of the information and no information tests (indicated

in blue and circled) of the texture of the chicken samples. (b) Principal component analysis (PCA) bi-plot indicating the position of the

sensory attributes (indicated in red), in relation to the four chicken meat samples (indicated in capital letters and black) and the degree of

liking of the information and no information tests (indicated in blue and circled) of the flavour of the chicken samples.

(BI – Broiler intensive; BFR – Broiler free range; HI – Ross X Potchefstroom Koekoek hybrid intensive; HFR – Ross X Potchefstroom

Koekoek hybrid free range)

BFR

BI

HFR

HI

Info

No Info

ChickenAroma

InitialJuiciness

ChickenFlavour

SustainedJuiciness

Tenderness

Residue

pH

%Driploss

%Cookingloss

WHC

ShearForce

%Moist

%Ash

%Fat

%Protein SFA

MUFA

PUFA PUFA:SFA

n-6:n-3

-15

-10

-5

0

5

10

15

-20 -15 -10 -5 0 5 10 15 20 25

F2 (3

4.91

%)

F1 (45.44 %)


BFR

BI

HFR

HI

Info

No Info

ChickenAroma

InitialJuiciness

ChickenFlavour

SustainedJuicines Tenderness

Residue

pH

%Driploss

%Cookingloss

WHC

ShearForce

%Moist

%Ash

%Fat

%Protein SFA

MUFA

PUFA PUFA:SFA

n-6:n-3

-15

-10

-5

0

5

10

15

-20 -15 -10 -5 0 5 10 15 20 25

F2 (3

4.63

%)

F1 (47.05 %)



142

Socio-demographic information and correlation with preference

In any consumer study, socio-demographic data sourced from the consumer can be studied and

correlated with specific variables, thus enabling the clustering of consumers into different

categories or groups according to their different profiles (Geel et al., 2005). In this study gender,

age, race, income, current employment, education and consumption frequency of chicken meat

were obtained from each consumer. In the ANOVA table (Table 7.4) the significant interactions

are indicated in bold. There was a significant interaction (P ≤ 0.05) for

Education*Genotype*Treatment for both texture and flavour which was then further investigated in

the PCA plots (Fig. 7.4a and b). This section will not be discussed here, but rather in the “further

analysis with segmentation” section - where the specific demographic factor(s) that had an effect

will be discussed.

Fig. 7.4a and b indicate that the consumers with an academic degree preferred the Hybrid

intensive and free range chicken samples more and that the consumers without a degree and only

with a Gr.12 diploma or less were more inclined to prefer the Hybrid intensive and Broiler free

range samples.

It was expected that the consumers with a degree would prefer Hybrid free range reared

products more, since they would have more knowledge of rearing systems and the type of bird

used in the production system. They would know that free range rearing could be more harmful to

broilers than intensive for which they are specifically genetically selected for and that a more tough

bird i.e. Hybrid would be more suitable for free range rearing. The opposite was expected from the

consumers without a degree, since it was assumed that they would not have the knowledge of

rearing systems and type of chicken used.

Table 7.4 ANOVA table of the overall linking for texture and flavour

DF Texture Flavour

Education 1 0.1257 0.5382

Consumer 98 <.0001 <.0001

Genotype*Treatment 3 0.0039 0.0073

Information 1 0.0078 0.2263

Genotype*Treatment*Information 3 0.0507 0.068

Education*Genotype*Treatment 3 0.0152 0.0008

Education*Information 1 0.2902 0.2246

Consumer*Genotype*Treatment (Education) 294 <.0001 <.0001

Consumer*Info (Education) 98 0.0636 0.0076

Degrees of freedom (DF) Significant interactions are indicated in bold.


143

Figure 7.4 Principal component analysis (PCA) bi-plot for the four chicken samples with regard to degree of liking of (a) texture and (b) flavour.

Samples are indicated as the scores in green and education as loadings in red. The PCA bi-plots explain 100.00% and 100.00% of the

variance respectively. (Degree – Consumers with a degree; Gr. 12 – Consumers with a Gr. 12 diploma; BI – Broiler intensive; BFR – Broiler

free range; HI – Ross X Potchefstroom Koekoek hybrid intensive; HFR – Ross X Potchefstroom Koekoek hybrid free range)

BFR

BI

HFR

HI

Degree

Gr. 12

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5

F2 (4

1.66

%)

F1 (58.34 %)


BFR

BI

HFR HI Degree Gr. 12

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

F2 (3

3.48

%)

F1 (66.52 %)



144

Cluster analysis of consumer liking data

The degree of liking results for the total consumers have already been discussed earlier (Fig. 7.3),

however, market researchers are usually interested to explore sub-segments of consumers within

a larger group of consumers (Parpinello et al., 2009). To determine whether the consumers’

degree of liking scores of this study would result in different clusters, a clustering technique was

performed on the full data set of the degree of liking scores. This technique identified three

clusters for this study, namely:

• Cluster 1: Consumers inclined to strongly favour free range reared chicken meat

• Cluster 2: Consumers inclined to strongly favour intensive reared chicken meat

• Cluster 3: Consumers inclined to equally favour free range and intensive reared chicken

meat

A PCA was done using the above-mentioned cluster data to see how the respective

clusters of consumers associate with the four different samples tested in a blind scenario (non-

informed) and informed scenario. According to Fig. 7.5(a) Cluster 1, representing 37% of the total

group of consumers, associate with all the free range meat samples, whether it was with

information or no information given, i.e. BFR and HFR. Cluster 2, representing 31% of the total

group of consumers, associate with all the intensive meat samples (BI and HI) and Cluster 3,

representing 32% of the total group of consumers, lies within the two identified groups indicating

that consumers equally preferred free range and intensive reared meat. These clusters indicate

that there is a group of consumers who will buy free range products, a group who will buy intensive

reared products and a group who would buy either free range or intensive reared products; usually

another factor like price or convenience would determine these consumers’ final decision making.

Further PCA analysis with the clusters and sensory attributes in Fig. 7.5(b) revealed once

again that all the consumers from Cluster 1, 2 and 3 are more inclined to favour meat that is more

juicy, tender and has a good chicken flavour and aroma.


145

Figure 7.5 (a) PCA bi-plot of the association of liking scores of the four chicken samples and three clusters of consumers. The PCA bi-plot explains

87.20% of the variance. (b) Association between sensory attributers and consumer liking for all identified clusters. The PCA bi-plot

explains 76.30% of the variance.

(BI Info – Broiler intensive with information; BI No – Broiler intensive with no information; BFR Info – Broiler free range with information;

BFR No – Broiler free range with no information; HI Info – Ross X Potchefstroom Koekoek hybrid intensive with information; HI No – Ross

X Potchefstroom Koekoek hybrid intensive with no information; HFR Info – Ross X Potchefstroom Koekoek hybrid free range with

information; HFR No – Ross X Potchefstroom Koekoek hybrid free range with no information)

BF No BF Info

HF No

HF Info

BI No

BI Info

HI No

HI Info

Cluster 1: Favour free range meat

Cluster 2: Favour intensive meat

Cluster 3: Favour free range and intensive meat

-3

-2

-1

0

1

2

3

-4 -3 -2 -1 0 1 2 3 4

F2 (3

6.18

%)

F1 (51.02 %)


BF Info

BF No

BI Info BI No

HF Info HF No

HI Info HI No



Cluster 3: Favour free range and intensive meat

ChickenAroma

InitialJuiciness

ChickenFlavour

SustainedJuiciness

Tenderness Residue

pH

%Driploss

%Cookingloss

WHC ShearForce

%Moist

%Ash

%Fat

%Protein SFA

MUFA

PUFA PUFA:SFA n-6:n-3

-20

-15

-10

-5

0

5

10

15

-20 -15 -10 -5 0 5 10 15 20 25

F2 (3

5.09

%)

F1 (41.21 %)



146

Consumer options and perception on chicken in general

In research where sensory attributes and degree of liking of a selection of chicken meat are tested,

general opinions on the products and related aspects regarding the products are usually also

investigated (Mueller & Szolnoki, 2010). In this study the group of consumers were also surveyed

on their general opinions or perceptions on the consumption and purchasing of chicken, as well as

the factors that drive these opinions (Table 7.5). These associated factors were tested on a 9-

point hedonic category scale and opinions on a three point scale i.e. “yes”, “no” and “not sure” as

indicated in Table 7.5 (Green & Srinivasan, 1978). The group of 100 consumers, all residents of

the Western Cape, were sourced to include male and female consumers. ANOVA were firstly

performed on the options of the total group of consumers.

Table 7.5 Range of general opinions influencing the purchase and consumption of chicken Opinions and associated factors tested Scale used Short title

Importance of price

1 = Not important 9 = Extremely important Price

Appropriate outlets for the purchasing of chicken

Supermarket Fresh produce market Directly from farmer

1 = Not appropriate 9 = Extremely appropriate Places purchased

Importance of intensive production

1 = Not appropriate 9 = Extremely appropriate Intensive

Importance of free range production

1 = Not appropriate 9 = Extremely appropriate Free range

Free range taste better than intensive

Yes No I am not sure

Taste

Free range is leaner than intensive


Leaner

Free range is healthier than intensive


Healthier

Free range is juicier than intensive


Juicier

Free range is more tender than intensive


More tender

Opinions and perception of the total group of consumers on chicken purchasing and consumption

It is well known that there are product-specific aspects that drive the consumer’s purchasing or

deciding process (Grunert, 2007). From the ANOVA results in Table 7.6 it is clear that price

(P ≤ 0.05) is a very important purchasing factor for consumers when considering chicken as menu

item. Also important is the place of purchase. This group of consumers indicated that they prefer

the supermarket (P ≤ 0.05) as a more favourite place of purchasing, and more so than a fresh


147

produce market or directly from the farmer. These results clearly indicate the convenience factor

of the supermarket above that of the fresh produce market or the farmer. From Table 7.6 it can

also be seen that consumer perception of free range reared meat plays an important role in

purchasing, more so than intensive (P ≤ 0.05) reared meat.

The results of the consumers’ opinions and perceptions on the positives of free range

chicken meat are depicted in Fig. 7.7. According to Fig. 7.7 it is clear that consumers are positive

towards free range meat. More than 50% of the consumers think that free range reared chicken

meat is healthier than intensive reared chicken meat and more than 40% the consumers think that

free range reared chicken meat tastes better and is leaner than intensive reared chicken meat. On

the question whether free range chicken meat is more juicy and tender, the consumers perceived it

to be either “yes” or “no” or “not sure” in similar proportions (Fig. 7.7). The same results were also

found by other researchers (Verbeke & Viane 1999; Yeung & Morris, 2001; Harper & Makatouni

2002; Grunert et al, 2004; Greene et al., 2005 as cited by Fanatico et al., 2005; Fanatico et al.,

2007; Castellini et al., 2008; Branciari et al., 2009).

In a PLS (partial least squares) regression (Fig. 7.8) the opinion of the consumers (X) were

regressed on the cluster liking scores (Y). This revealed that the consumers from cluster 1 (who

prefer free range meat) strongly inclined to believe that free range is leaner, more juicy, healthy

and tender than intensively reared meat. They were, however, unsure if free range reared chicken

meat had a better flavour than intensively reared meat. These consumers also knew the answer to

the definition of free range and intensively reared chicken meat. In contrast to cluster 1, the

consumers from cluster 2 think that intensively reared chicken meat tastes better, is more juicy,

healthy and tender than free range reared chicken meat. These consumers were also unsure if

intensive reared chicken meat is leaner, healthier or more tender than free range reared chicken

meat. The consumers from cluster 3 said either “yes”, “no” or “are not sure” to the different

opinions. This places them in a position where that they would prefer either free range reared or

intensively reared chicken meat. The consumers from clusters 3 were also the people who did not

know the difference between free range and intensive reared chicken meat.

These opinions or perceptions of the consumer play a very important role in the final

decision making process of the consumer and would sometimes influence a consumer to buy a

specific type or “brand” of chicken meat.


148

Table 7.6 ANOVA table indicating purchasing factor importance

Question for purchasing factor Mean ± SD

Price 6.9a ± 1.69

Places purchased

Supermarket 6.3 b ± 2.14

Fresh produce market 5.5 c ± 2.12

Directly from farmer 4.5 d ± 2.67

Intensive 4.1 d ± 2.23

Free range 6.1bc ± 2.41

LSD 0.60 abMeans incolumnswith different superscripts are significantly different at P ≤ 0.05

Figure 7.7 Consumers’ opinion or perception on free range reared chicken meat.

48 46

58

37 39

29 41

30

28 25

23 13 12

35 36

0

10

20

30

40

50

60

70

80

90

100

Better taste Leaner Healthier Juicier More tender

Perc

enta

ge (%

)

No

Not Sure

Yes


149

Figure 7.8 PLS plot indicating the driving forces for consumer decision making in their

specificclusters. The map was obtained using partial least square regression, where the opinions

or perceptions (X-space) were regressed onto the cluster data (Y-space). (Taste_Y – consumers

who perceive that free range taste better than intensive; Taste_U - consumers who are unsure if

free range taste better than intensive; Taste_N – consumers who believe that free range do not

taste better than intensive; Leaner_Y - consumers who perceive that free range is leaner than

intensive; Learner_U - consumers who are unsure if free range is leaner than intensive; Leaner_N

– consumers who believe that free range is not leaner than intensive; Health_Y - consumers who

perceive that free range is healthier than intensive; Health_U - consumers who are unsure if free

range is healthier than intensive; Health_N – consumers who believe that free range is not

healthier than intensive; Juicier_Y - consumers who perceive that free range is juicier than

intensive; Health_U - consumers who are unsure if free range is juicier than intensive; Health_N –

consumers who believe that free range is not juicier than intensive; Tender_Y - consumers who

perceive that free range is more tender than intensive; Tender _U - consumers who are unsure if

free range is more tender than intensive; Tender _N – consumers who believe that free range is

not more tender than intensive; FR_Wrong – Consumers who got the definition of free range

wrong; FR_Right – Consumers who got the definition of free range right; CI_Wrong – Consumers

who got the definition of intensive wrong; CI_Right – Consumers who got the definition of intensive

right.)

CI_Correct

CI_Wrong

FR_Correct

FR_Wrong

TASTE_Y

TASTE_N

TASTE_U

LEANER_Y

LEANER_N

LEANER_U

HEALTH_Y

HEALTH_N HEALTH_U

JUICIER_Y

JUICIER_N

JUICIER_U

TENDER_Y

TENDER_N

TENDER_U



Cluster 3: Favour

free range and intensive meat

-0.5

-0.25

0

0.25

0.5

-0.75 -0.5 -0.25 -1E-15 0.25 0.5 0.75

t2

t1

Correlations on axes t1 and t2

X Y


150

CONCLUSIONS

The aim of this study was to gain information on consumers’ degree of liking towards the two

different genotypes i.e. Broiler and Hybrid hybrid reared intensively or in a free range system.

Consumers’ perception and opinions on free range and intensive reared products were also tested.

Overall, genotype had a greater impact on the consumers’ degree of liking than production

system, but when information was given on the production system of a chicken product, the

consumers tend to lean more towards a free range reared product than an intensively reared

product. Correlation with the sensory results indicated that juiciness, tenderness, chicken aroma

and chicken flavour are the main drivers of liking. Furthermore, three different clusters of

consumers were identified, when investigating the degree of liking of the consumers. The clusters

were described as:

• Cluster 1: Consumers that prefer free range reared chicken meat

• Cluster 2: Consumers that prefer intensive reared chicken meat

• Cluster 3: Consumers that prefer both free range and intensive reared chicken meat

These clusters cleary indicate that there are two extreme groups, i.e. a group of consumers

who is loyal to free range reared chicken meat and then also a group who will definitely buy

intensive reared chciken meat when given the option. The third cluster is a group of consumers

who are not loyal to a specific “brand” and neither prefer free range nor intensive reared chicken

meat, regardless of the information given. This group will most probably be influenced by other

factors, such as price, place of purchase or general conveniece.

From this study it would seem that Hybrid would be the better alternative for free range

rearing and the success of this type of chicken would be ascribed to successful marketing and

education endorsing this type of chicken and rearing environment to the consumers.

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153

CHAPTER 8

GENERAL CONCLUSIONS AND RECOMMENDATIONS

The modern consumer tends to be conscious of animal welfare and general health, requests

products that are environmentally friendly, promote sustainability, have nutritional value, as well as

excellent meat quality traits. Therefore the meat industry is constantly facing new challenges, not

only driven by the consumers’ preferences and concerns, but also economic factors and

environmental changes. One such consumer preference that is growing is that for free range

produced poultry meat and products. Free range poultry producers need to understand the

expectations and potential willingness of target consumers to pay a premium price for this product

so as to assess whether it is possible to offset the higher cost of production associated with these

chickens. The costs are higher as some of the production parameters associated with a free range

system differ from that linked to an intensive production system; one of these factors is that the

free range system requires slower growing genotypes resulting in an older bird being slaughtered.

In this investigation, the effect of slower growing indigenous Koekoek (and their hybrid) compared

to commercial Broilers reared in either an intensive or free range system were evaluated in terms

their meat quality parameters.

The results of this study indicate that genotype had a much larger effect than production

system on the morphological and growth properties of chicken meat, as well as on the sensory

characteristics. As expected, the broiler genotype, which is specifically bred for efficient growth,

feed efficiency and meat yield, thrived in these aspects compared to the Hybrid and Koekoek

genotypes, but despite the poorer growth performance and efficiency of the medium growing

Hybrid birds, they had a lower mortality and fewer leg disorders than the broiler. Additional to

these factors, the hybrid free range reared chickens had higher thigh, drumstick and wing yields

than the broiler, which is beneficial to the industry, since South African consumers prefer dark meat

over white meat. The Hybrid chicken scored significantly higher in both flavour and aroma than the

Broiler and Koekoek genotypes.

With regard to the physical characteristics and chemical composition of the meat, it would

seem that the effect of production system was more pronounced than the effect of genotype.

Although production system differences were found in the pH values, CIE a*, CIE b* CIE L* colour

values, fat and protein content in selected portions; the most significant of these were the pH and

CIE*a values. The free range chicken meat was found to be less red in colour and this could be

due to the lower muscle pH caused by minor ante mortem stress during the capture and carrying of

the birds. Meat colour is an indicator of freshness and quality and one of the most important

factors that influence consumer decision making at the point of purchase. Although chicken is

classified as a “white” meat, with a low CIE a* value, consumers might be influenced by the pale

white colour of the free range chicken meat. Rearing chickens in a free range environment


154

increased the total polyunsaturated fatty acids (PUFA) and polyunsaturated to saturated fatty acid

ratio (PUFA:SFA), and can be considered more favourable to the human health than the

intensively reared chicken meat.

Consumers’ perceptions, attitudes and beliefs are very important features that must be

considered by the agricultural sector, since this is a very strong driving force for the industry and

determinethe sustainability and feasibility of a product in the market. From a South African

perspective of chicken meat, it was found that genotype had a greater impact on the consumers’

degree of liking than production system. However, when information was given on the production

system of the chicken product, the consumers tend to lean more towards a free range reared

product than an intensively reared product. Three different clusters of consumers were identified

after tasting chicken meat in a “blind”analysis:

• Cluster 1: Consumers that prefer free range reared chicken meat

• Cluster 2: Consumers that prefer intensively reared chicken meat

• Cluster 3: Consumers that prefer both free range and intensive reared chicken meat

These clusters cleary indicate that there are groups of consumers who will stay loyal to a

specific “brand” and a group who won`t, and usually, factor(s) such as price, place of purchase or

convenience would influence their final decision for purchasing. The main sensory drivers for

consumer’s preference towards chicken meat are juiciness, tenderness, chicken aroma and

chicken flavour.

The results seem to indicate that the Hybrid hybrid would be a good alternative genotype

for free range rearing in South Africa.

From this study the following recommendation can be made to the South African poultry

meat industry: for the poultry industry to compete in a free range or health-driven market, a hybrid

or medium growing bird should be used for free range rearing to achieve optimum profit. Excellent

marketing practices should be in place to promote free range chicken products; for example, an

educational program could be initiated to inform consumers about the differences, positive and

negative aspects of free range production systems. However, to improve on this study and to

thoroughly understand the full impact of a production system and genotype on the sensory,

chemical, nutritional and instrumental quality characteristics and consumer preference of chicken

meat, it is recommended that season (summer, winter, spring and autumn) and the effect of

gender (male and female) should be quantified. Another aspect that would prove interesting is the

analysis of different crosses, to find the optimum hybrid for free range production, or even the

development of a dual purpose genotype, combining both egg and meat production, which could

potentially fulfil free range production if demands on production are not as high as for intensive

production. A more in-depth study on muscle fibre type and its effect on the muscle chemical

composition and quality will also provide interesting information in understanding the role of muscle

fibre types in meat quality as it was postulated that the fibre types may change as the free range

birds have more exercise. Larger and more representative consumer panels that include race and


155

culture as main effects can also be explored to gain more insight into the perceptions and

preferences of the entire population of Southern Africa.


156

ADDENDUM A


157

CONSUMER TESTING OF CHICKEN

Please circle the applicable answer Judge no. ___

GENDER: AGE:

Male / Female 18-23 / 24-29 / 30-39 / 40 – 49 / 50+

RACE GROUP: EDUCATION:

Black / Coloured / White / Indian / Other:_____________________ Grade 11 or less / Grade 12 (Matric) / Diploma or Degree

WHAT IS YOUR CURRENT EMPLOYMENT: INCOME GROUP: Please give an indication of your MONTHLY or YEARLY income

Student / Assistant/ Administrative / Professional / Retired / Unemployed Monthly: <5,000 / 5,001 - 10,000 / 10,001 - 30,000 / >30,000

Other:_______________ Yearly: <60,000 / 60,001 - 120,000 / 120, 001 - 360,000 / >360,000

HOW OFTEN DO YOU PURCHASE BUY CHICKEN: HOW OFTEN DO YOU CONSUME CHICKEN:

More than 3x per week / 1-2x per week / 2x per month / Approx 4x per year / NEVER More than 3x per week / 1-2x per week / 2x per month / Approx 4x per year / NEVER

WHICH OF THE FOLLOWING STATEMENTS BEST DESCRIBE THE 2X METHODS OF CHICKEN PRODUCTION CURRENTLY USED IN SA? Please CIRCLE the corresponding number next to the preferred answer: HIGHLY COMMERCIALIZED, INTENSIVE PRODUCTION SYSTEM 1. Method of farming where pesticides or artificial chemicals are used and animals cannot roam freely. 2. Method of farming where no pesticides or artificial chemicals are used and animals can roam freely 3. Method of farming where pesticides or artificial chemicals are used and animals can roam freely FREE RANGE PRODUCTION SYSTEM 1. Method of farming where pesticides or artificial chemicals are used and animals cannot roam freely. 2. Method of farming where no pesticides or artificial chemicals are used and animals can roam freely. 3. Method of farming where pesticides or artificial chemicals are used and animals can roam freely

Please turn to page 2


158

SET 1 DEGREE OF LIKING of 4x chicken samples

INSTRUCTIONS: Rinse your mouth with water between samples. Take a GENEROUS BITE from each sample. Rank the samples for DEGREE OF LIKING & CIRCLE the number next to the preferred answer

How do you like the

TEXTURE

of the chicken?

CODE CODE CODE CODE 9 Like extremely 9 Like extremely 9 Like extremely 9 Like extremely

8 Like very much 8 Like very much 8 Like very much 8 Like very much

7 Like moderately 7 Like moderately 7 Like moderately 7 Like moderately

6 Like slightly 6 Like slightly 6 Like slightly 6 Like slightly

5 Neither like nor dislike 5 Neither like nor dislike 5 Neither like nor dislike 5 Neither like nor dislike

4 Dislike slightly 4 Dislike slightly 4 Dislike slightly 4 Dislike slightly

3 Dislike moderately 3 Dislike moderately 3 Dislike moderately 3 Dislike moderately

2 Dislike very much 2 Dislike very much 2 Dislike very much 2 Dislike very much

1 Dislike extremely 1 Dislike extremely 1 Dislike extremely 1 Dislike extremely

How do you like the

TASTE

of the chicken?

CODE CODE CODE CODE

9 Like extremely 9 Like extremely 9 Like extremely 9 Like extremely









Refresh your mouth with water & Turn to page 3 for more samples


159

SET 2 DEGREE OF LIKING of 2x Intensive + 2x Free Range chicken samples

INSTRUCTIONS: Rinse your mouth with water between samples. Take a GENEROUS BITE from each sample. Rank the samples for DEGREE OF LIKING, CIRCLE the number next to the preferred answer.

Sample A Sample B Sample C Sample D

Existing genotype +

Intensively reared

Existing genotype +

Free Range

New indigenous genotype +

Intensively reared

New indigenous genotype +

Free Range

Indicate how you like the

TEXTURE

of the chicken










Sample A Sample B Sample C Sample D

Indicate how you like the

TASTE

of the chicken










Please turn to page 4


160

General questions on chicken meat Please indicate your OPINION on the following…….. Please Circle YES, NO OR I AM NOT SURE

Does Free Range chicken TASTE better than normal chicken? Yes / No / I am not sure

Is Free Range chicken LEANER than normal chicken? Yes / No / I am not sure

Is Free Range chicken HEALTHIER than normal chicken? Yes / No / I am not sure

Is Free Range chicken JUICIER than normal chicken? Yes / No / I am not sure

Is Free Range chicken MORE TENDER than normal chicken? Yes / No / I am not sure

How important are the following ASPECTS are when you BUY CHICKEN? 1____2____3____4____5____6____7____8____9

NOT IMPORTANT NOT SURE EXTREMELY

IMPORTANT

PRICE of chicken meat 1____2____3____4____5____6____7____8____9

PLACE of purchase, i.e.

1. Supermarket. 1____2____3____4____5____6____7____8____9

2. Fresh produce market 1____2____3____4____5____6____7____8____9

3. Directly from the Farmer 1____2____3____4____5____6____7____8____9

Chickens must be reared in an INTENSIVE COMMERCIAL production system 1____2____3____4____5____6____7____8____9

Chickens must be reared in an FREE RANGE production system 1____2____3____4____5____6____7____8____9

ONLY ASWER THE FOLLOWING IF YOU BUY & CONSUME FREE RANGE CHICKEN

HOW OFTEN DO YOU CONSUME FREE RANGE CHICKEN? More than 3 times per week / 1-2 times per week / 2x per month / Approx 4 times a year / NEVER


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The effect of genotype and rearing system on chicken meat